linguistics-test: sentence has no primary verb
(1) arfle barfle gloop

SENTENCE_NT'arfle barfle gloop'

(2) beth is not a sailor

SENTENCE_NT'beth is not a sailor'
    VERB_NT'is not' {verb 'be' 3p s act IS_TENSE -ve}
    UNPARSED_NOUN_NT'beth'
    UNPARSED_NOUN_NT'sailor' {indefinite 'a' n/m/f nom/acc s}