sentence-->sentence(X).
sentence(X)-->noun_phrase(X),verb_phrase(X).

noun_phrase(X)-->determiner(X),noun(X).

verb_phrase(X)-->verb(X),noun_phrase(Y).
verb_phrase(X)-->verb(X).

determiner(_)-->[the].
determiner(_)-->[an].
determiner(_)-->[a].

noun(singular)-->[apple].
noun(singular)-->[pear].
noun(singular)-->[man].
noun(plural)-->[apples].
noun(plural)-->[pears].
noun(plural)-->[men].

verb(singular)-->[eats].
verb(singular)-->[likes].
verb(plural)-->[eat].
verb(plural)-->[like].

/*
noun(singular,[apple|R],R).
verb(plural,[like|R],R).
verb(singular,[likes|R],R).
verb_phrase-->verb.
verb_phrase(X)-->verb(X).
verb_phrase(X,S1,R):-verb(X,S1,R).
verb_phrase(X,S1,R):-verb(X,S1,S2),noun_phrase(Y,S2,R).
*/