One a day
Daily Stack
One puzzle a day, five rungs, ascending from tier one to tier five. One shot per rung. Your result is shareable, so a stack you cleared is a stack you can compare.
Play. Learn. Level up.
Pick the word that actually fits
Synonym Stack shows you a word, its part of speech and a real sentence, then asks which of four words could replace it there. Every answer tells you what the word means and why the tile you nearly picked was wrong. This site is the library it plays from, 3,600+ pairs deep, open to read.
3,600+ audited pairs5 difficulty tiersiPhone
What this isSynonym Stack for iPhone
Audited pairs3,600+Every entry read and corrected by a human, one at a time
Word pages3,000+One page per word on this site, sense by sense
Reason lines1,900+Entries that explain why the closest wrong answer is wrong
Difficulty tiers5Foothills at the bottom, Summit at the top
Game modes5Daily Stack, The Climb, Classic, Blitz, Sudden Death
PriceFree*Ads included; Plus removes them by subscription
* Free to download with ads. Synonym Stack Plus removes them: $2.99 a week, $5.99 a month, or $49.99 a year. Every word figure above is counted from the bank when this page is built, then floored to the nearest hundred, because the bank keeps growing.
Inside the appiPhone
One word, four tiles, and a sentence that settles it
There is no typing, no timer you cannot see, and no trick answers. The whole game is a question about sense: given this word in this sentence, which of these four words could stand in its place.
The home screen
A day at a time, and a mountain behind it
Home carries the day: your streak, the level you are on, the five rung stack waiting, a daily challenge chest, and the words the journal has flagged for a second look. The tab bar underneath goes to the mountain, the library of word packs, and your own record.
Levelling up opens new shelves in the library, fifty words to a shelf. Progress follows you between devices through your own iCloud account, and there is no account to create with us at all.
See the five modes
Five ways to playFive modes, none of them a mockup
The same bank, five different kinds of pressure
Modes differ in what they cost you to be wrong. Pick the one that matches how much attention you have: a single careful stack, a long ascent, or sixty seconds of nerve.
The long game
The Climb
An ascent of Mount Lexicon, stage by stage, through nine painted worlds from the Forest of Verbs to the Celestial Word Observatory. Each stage is scored one to three stars, so a pass is not the same as a clean pass.
Sixty seconds
Blitz
Sixty seconds on the clock and as many words as you can stack. The difficulty ramps as the run goes on, so a long Blitz finishes somewhere near the Summit.
Two more ways to run itThe board on the Blitz card, without the clock
Classic
No clock at all, three lives, and a difficulty ramp that opens near your earned level rather than at the bottom. This is the mode for reading the sentence properly.
Sudden Death
One life. The first wrong tile ends the run. Same bank, same sentences, and a very different relationship with the near misses.
Why it teachesThree things every question does
A quiz tests you. This is built to tell you why.
01
A sentence, before anything else
Every question opens with the word, its part of speech and an example sentence. A word on its own has no single meaning, so the sentence is what makes one right answer possible. That is a contract, not a decoration: no entry ships without one.
02
The meaning and the reason, after every tap
Answer correctly and you still get told what the word means. Answer wrongly and you get the same thing plus the reason: which sense the word you picked belongs to, and why the true synonym carries this one instead. Most of the bank carries that reason line.
03
The words you missed come back
The Word Journal tracks every word you have met, mastered, or flagged to revisit. Words you got wrong return in a revision drill and are worth extra experience when you win them back, so a miss is a lead rather than a loss.
The word libraryEvery word in the bank →
The whole bank is on this website, not just in the app
3,600+ pairs were built from WordNet 2025 and then read by a human, one at a time, to throw out the ones that were not fair. Every surviving pair has a page here: the sense, the sentence, the true synonym, and the reason its nearest wrong answer is wrong.
pathnounwaya course of conductFoothillsHas a reason linefadeverbmeltbecome less clearly visible or distinguishableTreelineHas a reason linegizmonoungimmicksomething unspecified whose name is either forgotten or not knownRidgelineHas a reason lineimpaleverbspikepierce with a sharp stake or pointHigh CampHas a reason linewhirnounbirrsound of something in rapid motionSummitHas a reason line
Synonym Stack Plus
What a subscription actually buys
The whole game is playable free. Plus removes the advertising and opens the parts of the library the free tier keeps behind a lock. Prices below are the App Store prices, and the trial applies where it says it does and nowhere else.
No ads anywhere
The banners and the interstitials go, in every mode.
Free revives
Revive a run without watching anything, in Classic, Blitz and Sudden Death.
The whole Daily Archive
Every past Daily Stack, not just the most recent teaser.
All Plus word packs
The locked shelves in the Library of the Mountain open.
Weekly$2.99No free trial on this plan
Monthly$5.997 day free trial
Annual$49.997 day free trial
Subscriptions are handled by Apple and renew until you cancel, which you do in your own App Store settings rather than by asking us. The full terms are on the terms page.
The mountain of words is waiting
Read the library here, then climb it on your phone. Five rungs a day, a reason under every answer, and a journal of every word you have met.
Get Synonym Stack freeFree with ads on iPhone. Synonym Stack Plus removes them: $2.99 a week, $5.99 a month or $49.99 a year, with a 7 day free trial on the monthly and annual plans.
