The main word of a phrase modified by other words is the headword.i.e.an honest man in this phrase man is a headword.usually it lies in noun phrase,noun clause,verb phrase,adj.phrase,adv.phrase.
How to recognize headword:
1.noun phrase as headword:the noun used in the noun phrase is a headword.it can be used as subj.and obj.
a.noun phrase as headword as subject:an honest boy can succeed.Here boy a headword.
b.noun phrase as headword as object:we honour a learned man.
Sometimes1.noun infinitive phrase may be the headword.i.e.to tell a lie is a sin.2.compound subj.as headword:if there are more word liked by and,or,but,it is compound subject.It is the headword also.3.noun clause as headword:a noun clause used as a subject in a sentence is a headword.i.e.That he is honest is true
c.verb phrase as headword:there are av and p.v in a verb phrase and the p.v. of a verb phrase is the headword..i.e.He has been playing.here playing is the headword.
d.adj.phrase as headword:he is quite hopeful of his success.Here hopeful is a headword.
e.adv.phrase as headword:Ice was all around them.Here around is a headword.