sentence(S1,R):-noun_phrase(S1,S2),verb_phrase(S2,R).

noun_phrase(S1,R):-determiner(S1,S2),noun(S2,R).

verb_phrase(S1,R):-verb(S1,S2),noun_phrase(S2,R).
verb_phrase(S1,R):-verb(S1,R).

determiner([the|R],R).
determiner([an|R],R).
determiner([a|R],R).

noun([apple|R],R).
noun([pear|R],R).
noun([man|R],R).

verb([eats|R],R).
verb([likes|R],R).
/*
sentence([a,man,eats,an,apple],[])
*/