shī yǔ
to let slip
loss of speech (e.g. as a result of brain damage)
aphasia
shī yǔ zhèng
aphasia or aphemia (loss of language)
jìn xíng xìng shī yǔ
progressive aphasia
gradual loss of speech
yuán fā xìng jìn xíng xìng shī yǔ
primary progressive aphasia (PPA), speech disorder (sometimes related to dementia)