think vs reckon

think is a noun but reckon is not a noun.

Word	Noun	Adjective	Verb	Adverb
think	Yes	No	Yes	No
reckon	No	No	Yes	No

As verbs, reckon is a hyponym of think; that is, reckon is a word with a more specific, narrower meaning than think:

As verbs, think and reckon are synonyms defined as:

Other synonyms of think include guess, imagine, opine, suppose.

think (noun)	reckon (noun)
an instance of deliberate thinking

think (verb)	reckon (verb)
bring into a given condition by mental preoccupation	deem to be
use or exercise the mind or one's power of reason in order to make inferences, decisions, or arrive at a solution or judgments	make a mathematical calculation or computation
judge or regard; look upon; judge	expect, believe, or suppose
recall knowledge from memory; have a recollection	judge to be probable
expect, believe, or suppose	have faith or confidence in
have in mind as a purpose	take account of
be capable of conscious thought
focus one's attention on a certain state
decide by pondering, reasoning, or reflecting
ponder; reflect on, or reason about
have or formulate in the mind
dispose the mind in a certain way
imagine or visualize