Acumo app icon
AcumoiPhone, iPad and Mac

The English words and phrases you keep mixing up.

Most vocabulary apps teach words you already half-know. Acumo works on the pairs that actually trip you up: adverse and averse, imply and infer, discreet and discrete. Open any word and it shows what you will confuse it with and the one line that separates them, then drills the pair until the difference sticks.

Coming soon to the App Store

Free to use, with no ads and no subscription. Works entirely offline.

Acumo's entry for adverse: pronunciation, a formal tag, the meaning and an example, then five words you might confuse it with, each labelled with why: averse, used wrong; diverse and perverse, prefix pairs; advert and advice, near sounds.
8,500+
words & phrases
4,500+
confusable pairs
650+
sentence frames
4
gloss languages
Why this one

Built on confusion, for people past the basics

Most vocabulary apps teach you more words. Acumo teaches the difference between words you already know.

Built on confusion

Every kind of mix-up drives the app: homophones, near-homophones, look-alikes, prefix pairs, usage traps and phrasal-verb families. That is the product, not a feature bolted onto one.

Not a dictionary, not for beginners

Written for B2 to C2. No streaks, no XP, no cartoon mascot. Nuance is the whole point, so the app talks to you like an adult, not a beginner.

Private and offline

No account, no tracking, no data collected. The entire collection ships inside the app and everything runs on your device.

One fair price

Free is complete, not crippled: the confusable engine is never for sale. Pro is one purchase, never a subscription.

The difference

What you will confuse it with, and why

Every word in Acumo can carry a strip of the words you are most likely to mix it up with, each labelled with the reason they collide: the same sound, a near sound, a look-alike spelling, a swapped prefix, or two words close enough in meaning to be used wrongly.

Sound, spelling and prefix relations are computed from the words themselves, not typed in one by one. Open a pair and Acumo sets the two side by side with the line that separates them. All of it is free.

adverse/averse

Used wrong
Adverse describes conditions or effects that work against you: adverse weather, an adverse reaction. Averse describes a person's unwillingness, and takes to: averse to risk.
The separating line, as Acumo shows it on the comparison screen.
Acumo's comparison of adverse and averse side by side, each with its pronunciation, meaning and example, above a card marked Used wrong that holds the line separating them, and a Drill this pair button.

Why two words collide

Every chip names its reason. One live pair for each, with the line the app gives it.

  • Same sound

    discreet / discrete

    Identical sound — spelling is the only clue.

  • Near sound

    affect / effect

    One phoneme apart. The ear will not do this for you.

  • Looks alike

    later / latter

    One letter apart, and they mean nothing alike.

  • Prefix pair

    allude / elude

    Different prefix, identical ending — the eye slides straight past it.

  • Used wrong

    imply / infer

    Close in meaning, not interchangeable.

  • Same family

    break down / break up

    Same verb, different particle — and a different meaning.

See what is inside
Free, in full

Free is complete, not crippled

The whole collection and the whole confusable engine are free, with no ads and no lock. You can learn with Acumo for as long as you like without paying.

Drills that make you choose

Four card types, including discrimination: one sentence, two confusables, and you pick the one that fits. Drill any pair straight from its comparison, and leave a long drill to pick up where you stopped.

A discrimination card asking which one fits: The drug was withdrawn after patients reported blank reactions to the second dose. Adverse is marked correct over averse, and the answer shows its meaning, the example and the separating line, with Hard, Good and Easy below.

A miss ends in an action

Acumo is a curated collection, not every word in English. Search for something it does not have and one tap adds it to your list, with your own meaning and example if you want them. On iPhone and iPad, the share extension does the same from any app.

A search for perfunctory, which reads: perfunctory isn't in the collection yet, with a button below, Add it to my list.

Collections to start from

Homophone sets, phrasal verbs, idioms, collocations, sentence frames, prefix pairs and spelling traps, plus every entry from A to Z, so there is something to drill from the first launch.

The Collections screen: All entries, then themed sets with their counts, sentence frames, idioms, phrasal verbs, collocations and homophone sets.

A gloss in your language

One short gloss beside the English, in Persian, Spanish, Brazilian Portuguese or Arabic. The first language you pick is free, and right-to-left scripts read as they should.

The entry for auspicious with its meaning in English and, beneath it, the Persian gloss written right to left, then an example and one word it is confused with: suspicious, looks alike.

The confusable engine, all of it

Every strip, every comparison and every separating line, on every word that has one. The engine is the reason the app exists, so it is never behind a paywall.

Plain meanings, real examples

Meanings written against a 2,800-word defining vocabulary, so the explanation is never harder than the word. A real example sentence on every entry, with the collocations that go with it: make a decision, not do a decision.

Pronunciation, offline

IPA on every entry, and every word spoken by your device's own voices, with no download and no connection.

One daily reminder

A single local notification on days when items are due. It asks for permission after your first finished review, never on launch.

Quiet progress

Known, learning and due as a status line, not a scoreboard. No streaks, no XP, no confetti.

Built for reading and for accessibility

VoiceOver, Dynamic Type and right-to-left text throughout, on iPhone, iPad and Mac.

In your language

Four gloss languages

One short gloss beside the English, never instead of it. Every pack covers the whole collection.

auspiciousshowing signs that something will go well in the future

  • Persianفارسی

    خوش یمن - مبارک - فرخنده

    Right to left
  • SpanishEspañol

    de buen augurio - prometedor - propicio - auspicioso

  • Brazilian PortuguesePortuguês

    auspicioso - de bom augúrio - propício

  • Arabicالعربية

    مبشّر بالخير - ميمون

    Right to left

The first language you pick is free; the others come with Pro, and Pro can show several on one entry.

Pro

One purchase, for the part that makes it stick

Pro adds no words and locks no pairs. It adds the retention system: when each item comes back, what you drill, and what you can take with you.

  • FSRS scheduling. Each word comes back on the day you are about to forget it, rather than on a fixed timetable. That timing is the FSRS algorithm, as used by Anki.
  • Weak-item targeting. Drills what you keep getting wrong, not what you already know.
  • Progress and retention. Your real retention rate, and the pairs you keep confusing.
  • Widgets. On iPhone and iPad: word of the day and your due count, gradeable without opening the app.
  • Every gloss language. All language packs beyond your first, shown together on the same entry.
  • Anki-compatible export. Your collection is yours: export it for Anki or as CSV, and leave whenever you like.
  • Backup and restore. Save your list, your own words and where each item sits in the schedule, and put it back on a new phone.

Pro buys the retention system and the extra languages, never the English collection or the confusable engine. Pay once, with no renewals and no ads, tied to your Apple ID so you can restore it after reinstalling.

What you get

Free and Pro, side by side

Everything you need to learn the pairs is in the free column. Pro is one purchase that adds the retention system, and it is never a subscription.

A comparison of what the free tier and the Pro unlock each include
CapabilityFreePro
The whole collection: 8,500+ words and phrasesIncludedIncluded
The confusable engine: every strip, comparison and separating lineIncludedIncluded
Meanings, examples, collocations, usage notes, pronunciationIncludedIncluded
Search, manual add, unlimited saved items, the share extension on iPhone and iPadIncludedIncluded
Four card types, including discriminationIncludedIncluded
When items come back1 · 3 · 7 · 21 daysFSRS
Weak-item targetingNot includedIncluded
Gloss languagesYour first pickAll four
Home Screen widget, on iPhone and iPadWord of the dayPlus due count
Progress and retentionNot includedIncluded
Anki-compatible and CSV exportNot includedIncluded
Backup and restoreNot includedIncluded

Pro is a single one-time purchase, restorable on any iPhone, iPad or Mac signed in to your Apple ID. The App Store shows the exact price in your region.

Coming soon to the App Store
iPhone, iPad and Mac

One app, on all three

Acumo is a single universal app, not three purchases. Buy Pro once and it unlocks on every iPhone, iPad and Mac signed in to the same Apple ID. Your list lives on the device you made it on, and a backup file carries it to another.

Acumo on iPad in landscape: the comparison of adverse and averse in two wide columns, each with its pronunciation, meaning and example, above the Used wrong card that holds the line separating them, and a Drill this pair button across the full width.

iPad, landscape

Requires iOS 17, iPadOS 17 or macOS 14 Sonoma, or later.

Questions

Straight answers

Is Acumo free?

Yes. The whole collection, the entire confusable engine, search, examples, pronunciation, unlimited saved items, all four card types, one daily reminder and one gloss language are free, with no ads. Pro is an optional one-time purchase that adds the retention system: FSRS scheduling, weak-item targeting, progress, widgets on iPhone and iPad, every gloss language, export and backup.

Is Pro a subscription?

No. Pro is a single one-time purchase, tied to your Apple ID so it restores on any iPhone, iPad or Mac you sign in to. There are no renewals. The App Store shows the exact price in your region.

Who is it for?

Learners at roughly B2 to C2: people who use English every day and still hesitate between affect and effect, or write discrete when they mean discreet. It assumes the basics and does not teach them.

What if a word I want is not there?

Acumo holds a curated collection rather than every word in English. Search for something it does not have and Add it to my list makes it part of your own set, searchable and reviewable like the rest. You can also email us to suggest it for the collection.

Where do the meanings come from?

They were written for Acumo, in plain English against a 2,800-word defining vocabulary, so a meaning is never harder than the word it explains. No dictionary's wording is reproduced. Pronunciation data comes from the CMU Pronouncing Dictionary, credited in the app under Settings, then About, then Acknowledgements.

Which languages are the glosses in?

Persian, Spanish, Brazilian Portuguese and Arabic, each complete across the collection. The first one you pick is free; the others come with Pro, which can also show several on the same entry. Persian and Arabic read right to left.

Does it work offline?

Entirely. The collection ships inside the app, pronunciation uses your device's own voices, and reminders are local notifications. Acumo makes no network calls, has no account and collects no data.

Which devices does it run on?

iPhone, iPad and Mac: iOS 17, iPadOS 17 or macOS 14 Sonoma, or later. It is one app, so Pro bought on one unlocks on the others signed in to the same Apple ID. The widget and the share extension are on iPhone and iPad.

Can I take my words with me?

Yes. Pro exports your collection in an Anki-compatible format or as CSV, and backs your list up to a file you keep, schedule included. Your collection is yours.

Know which one you mean

The collection and the whole confusable engine are free. No ads, no subscription, and it works entirely offline.

Coming soon to the App Store

Requires iOS 17, iPadOS 17 or macOS 14 Sonoma, or later.