彼の髪はますます薄くなった。

he; him; his; boyfriend

indicates possessive; nominalizes verbs and adjectives; substitutes for "ga" in subordinate phrases; (at sentence-end, falling tone) indicates a confident conclusion; (at sentence-end) indicates emotional emphasis; (at sentence-end, rising tone) indicates question

hair (on the head)

topic marker particle; indicates contrast with another option (stated or unstated); adds emphasis

increasingly; more and more; decreasingly (when declining); less and less

thin; pale; light; watery; dilute; sparse; weak (taste, etc.); slim (probability, etc.); small

to become; to get; to grow; to be; to reach; to attain; to result in; to prove to be; to consist of; to be composed of; to succeed; to be complete; to change into; to be exchanged for; to play a role; to be promoted; to do ...