line of thought vs thought

line of thought and thought both are nouns.

Word	Noun	Adjective	Verb	Adverb
line of thought	Yes	No	No	No
thought	Yes	No	No	No

As nouns, thought is a hypernym of line of thought; that is, thought is a word with a broader meaning than line of thought:

line of thought: a particular way of thinking that is characteristic of some individual or group
thought: the process of using your mind to consider something carefully

Other hypernyms of line of thought include cerebration, intellection, mentation, thinking, thought process.

line of thought (noun)	thought (noun)
a particular way of thinking that is characteristic of some individual or group	the process of using your mind to consider something carefully
	the content of cognition; the main thing you are thinking about
	the organized beliefs of a period or group or individual
	a personal belief or judgment that is not founded on proof or certainty