noun. In pathology, inability to form a grammatical sentence.

noun. The inability to form sentences by virtue of a brain disorder.

"_ -- Many children, long after they have overcome acataphasia and agrammatism, delight in inserting between words sounds, syllables, and words that do not belong there; e. g., they double the last syllable of every word and put an _eff_ to it: _ich-ich-eff_, _bin in-eff_, etc., or they make a kind of bleat between the words"

acalculia  

agrammatist  grammar  grammatical  

pitying  smidgen