Common Three-Letter Combos (Trigrams)
the · ing · ion · ent · tio
A trigram is a three-letter sequence. THE, ING, ION, ENT and AND recur so often that skilled typists execute them as a single burst — the highest-leverage chunks you can train.
The next level of chunking
Once bigrams feel automatic, trigrams are the natural next step: -ING endings, THE, and -TION turn up in a large fraction of English words.
Practicing them as units is far more transferable than isolated-key drills, because this is how words are actually built.
Tip: Master -ING and -TION — they end an enormous number of English words.