D. Geraint Lewis grew up in Ynysybwl and went to school in Pontypridd and university in Aberystwyth. A librarian by profession, he is a prolific author of books for Welsh learners, including Berfau: A Check-list of Welsh Verbs , Yr Ansoddeiriau: A Comprehensive Collection of Welsh Adjectives , Y Rhifolion: Welsh Numerals and Y Diarhebion: A Compendium of Contemporary Welsh Proverbs . He won the Tir na n-Og Award for the best children's book of the year (excluding fiction) for Geiriadur Gomer i'r Ifanc (Gomer Dictionary for Young People).