Thank you for the comprehensive explanation.

I had to change my 'long held belief' that vocabualry (from 'vocable': voice-able; utterance (including 'words' or diction (which gives rise to 'dictionary': all that express diction: articulation of words).

I short, 'eek, yak, yum,...' are (vocable) included in vocabulary but may not be included in 'diction' or dictionary because they don't have 'formal' ways to pronounce exactly.

I was wrong apparently ;-)