CSW21 vs TWL — Scrabble Dictionary Differences Explained

What Is CSW21?

CSW21 stands for Collins Scrabble Words 2021, the official word list sanctioned by the World English-Language Scrabble Players Association (WESPA). It is the standard dictionary used in all international Scrabble competitions outside North America, including the World Scrabble Championship.

CSW21 contains approximately 279,000 valid words, making it the larger of the two main Scrabble dictionaries. It includes:

• All words from the previous edition (CSW19) plus additions
• A broad range of words from British, Australian, New Zealand, and other varieties of English
• Many words that originated in other languages but have been adopted into English (e.g., "QI" from Chinese, "ZA" as an abbreviation for pizza, "AA" for a type of lava)
• Archaic and rare words that are nonetheless accepted in tournament play (e.g., "AE" for one, "FE" for a Hebrew letter)

CSW21 is updated approximately every two years by Collins in consultation with WESPA. The next edition will likely be CSW23 or CSW25. New words are added, and occasionally a few are removed, though removals are rare.

What Is TWL?

TWL stands for the Tournament Word List, also known as the NASPA Word List (NWL), published by the North American Scrabble Players Association. It is the standard dictionary used in Scrabble tournaments in the United States and Canada.

TWL contains approximately 100,000-120,000 valid words — significantly fewer than CSW21. It is based on the Official Scrabble Players Dictionary (OSPD) with additional words added for tournament play. The most current edition as of 2024 is NWL2023 (NASPA Word List 2023).

TWL is generally more conservative than CSW21. It excludes many words that are accepted in international play, particularly:

• Words of foreign origin that haven't been naturalised in North American English
• Archaic and very rare words
• Some British, Australian, and New Zealand spellings

Key Differences Between CSW21 and TWL

The most significant difference is size: CSW21 has roughly 2.5 times as many words as TWL. But the practical difference for players comes down to specific word categories:

Two-Letter Words

CSW21 has 127 valid two-letter words. TWL has fewer. Some key two-letter words in CSW21 that are NOT in TWL include:

• DA — A Nigerian Pidgin English word meaning "yes" or an informal variant of "there." Valid in CSW21, not in TWL.
• GI — A martial arts uniform. Valid in CSW21, not in older TWL editions (added in some recent ones).
• OK — Surprisingly, this was not in US Scrabble dictionaries for many years; it was a late addition.
• TE — A musical note (the seventh note of the scale in tonic sol-fa).
• ZA — Slang for pizza. In CSW21, may or may not be in TWL depending on edition.

This is a critical practical difference because two-letter words are the most frequently used words in Scrabble. Knowing the full CSW21 list gives you more parallel play options.

Q Without U Words

CSW21 includes many more Q-without-U words than TWL. In CSW21 you can play QI, QAT, QADI, QOPH, FAQIR, TRANQ, and several others. TWL has a smaller set. Our Q Without U guide covers all valid options in CSW21.

Bingo Words (7-Letter +)

Many 7-9 letter words in CSW21 are absent from TWL, particularly:

• Words with British spellings (e.g., COLOUR, FAVOUR, CENTRE — though many of these are not valid in Scrabble at all without the -S)
• Words from non-US English dialects
• Rare botanical and scientific terms
• Compound words more common in British English

Which Regions Use Which Dictionary?

• CSW21 (International): Used in the United Kingdom, Ireland, Australia, New Zealand, South Africa, India, Singapore, Malaysia, Kenya, Nigeria, and most other countries outside North America. Used at the World Scrabble Championship and all WESPA-sanctioned tournaments.
• TWL / NWL (North America): Used in the United States and Canada for all NASPA-sanctioned tournaments. Also used in many online Scrabble platforms for North American players.
• OSPD (Official Scrabble Players Dictionary): The commercial dictionary sold by Hasbro for home play in North America. TWL is based on OSPD but adds tournament-level words.

If you play on an online platform like Scrabble GO, Wordfeud, or Words With Friends, the dictionary varies by platform and region. Scrabble Solva uses CSW21 but offers Safe Mode as a cross-dictionary option.

Safe Mode — The Best of Both Worlds

Scrabble Solva's Safe Mode was designed specifically to solve the CSW21 vs TWL problem. When Safe Mode is enabled, the solver filters results to only show words that appear in both CSW21 and common everyday English usage. These are words that:

• Are valid in most Scrabble dictionaries
• Would be recognised by casual players
• Won't trigger challenges in mixed-dictionary games
• Include the most commonly played words in real games

Safe Mode is ideal for:

• Playing with friends or family who use a different dictionary
• Online play when you don't know what dictionary the platform uses
• Learning the game without needing to memorise obscure tournament words
• Casual games where the spirit of the game is more important than min-maxing the dictionary

The Tournament Scene — Why Dictionary Knowledge Wins Games

In competitive Scrabble, dictionary knowledge is a recognised skill category, just like rack management or board vision. Top tournament players know tens of thousands of words by heart and actively study word lists between games. The CSW21 vs TWL split means that international players have a much larger word pool to learn from — but also a harder learning curve.

Some tournament-specific dictionary facts:

• CSW21 specialists know approximately 50,000-80,000 words at the elite level, including thousands of bingos (7+ letter words) that don't exist in TWL.
• TWL specialists have a smaller word pool but still study extensively — the top US players know 30,000-50,000 words.
• The overlap between CSW21 and TWL is roughly 95% of commonly played words. The difference is in the edges — the obscure words, the rare bingos, and the two-letter words that give international players an edge in cross-dictionary games.
• Online crossover events where CSW21 players face TWL players are increasingly common on platforms like Internet Scrabble Club (ISC) and Woogles.io. In these games, the dictionary is typically agreed upon beforehand or the CSW21 list is used as the default.

Practical Tips for Cross-Dictionary Play

• Know your two-letter words: Learn the CSW21 set of 127. Even if your opponent uses TWL, knowing the extra CSW21-only two-letter words gives you advantages in parallel play.
• Use Safe Mode: When in doubt about which dictionary your opponent uses, play only words that appear in Safe Mode on Scrabble Solva. These are universally acceptable.
• Avoid obscure CSW21-only bingos: If you're playing a TWL opponent, don't attempt words like "AEROBIC" if you're not sure it's in TWL (it is, but many similar words aren't). Stick to common words.
• Challenge wisely: If you're playing under CSW21 rules, challenge aggressively — many words your North American opponent thinks are valid might not be in TWL, but they're fine in CSW21. And vice versa.
• Study the overlap: The words common to both dictionaries are the most valuable to learn because they're playable in any game, in any region, on any platform.

Dictionary Editions and Updates

Both dictionaries receive periodic updates. Here are the recent and upcoming editions:

• CSW19 (2019): Added approximately 2,000 new words. Removed a handful of outdated terms.
• CSW21 (2021): Added words reflecting modern vocabulary including pandemic-related terms. Current standard for international play.
• OWL / TWL 2015: The last major update to the North American tournament list before the NASPA restructuring.
• NWL2020 / NWL2023: Recent NASPA Word List editions. Added words like YUZU, BIPARTISAN, and others reflecting modern usage.

Scrabble Solva uses CSW21 as its primary dictionary and updates the word list when new editions are released. Safe Mode is maintained as a curated subset and may not always reflect the very latest additions from either dictionary.

Final Thoughts

The CSW21 vs TWL distinction matters most to tournament players and serious Scrabble enthusiasts. For casual players, the difference is minor — most common English words are valid in both dictionaries. Use Scrabble Solva's Safe Mode if you're unsure, turn it off if you want full CSW21 coverage, and remember: the best dictionary is the one everyone at the table has agreed to use.

If you're serious about improving, learn the full CSW21 list. It gives you the largest possible word pool and prepares you for any Scrabble game anywhere in the world.