Credits

Wordbank

Age of acquisition: roughly how old children are when they learn a word.

We use only age values derived from this data, never the word lists of the questionnaires.

Frank, Braginsky, Yurovsky and Marchman (2017). Wordbank: An open repository for developmental vocabulary data. Journal of Child Language.

• Licence: CC BY 4.0
• Source: Wordbank

Glasgow Norms

Age of acquisition: roughly how old children are when they learn a word.

Scott, Keitel, Becirspahic, Yao and Sereno (2019). The Glasgow Norms: Ratings of 5,500 words on nine scales. Behavior Research Methods.

• Licence: CC BY 4.0
• Source: Glasgow Norms

wordfreq

Word frequency: how often a word is used.

Robyn Speer. wordfreq 3.1.1.

• Data licence: CC BY-SA 4.0
• Code licence: Apache 2.0
• Source: wordfreq

CEFR-J Wordlist

The list of beginner (A1) English words.

The CEFR-J Wordlist Version 1.6. Compiled by Yukio Tono, Tokyo University of Foreign Studies. Retrieved from https://www.cefr-j.org/download.html on 16/10/2026.

• Free to use, including commercially, with acknowledgement of the source.
• Source: CEFR-J Wordlist