verb

• (transitive) To assess the similarities and differences between two or more things ["to compare X with Y"]. Having made the comparison of X with Y, one might have found it similar to Y or different from Y.
  "Compare the tiger's coloration with that of the zebra."
• (transitive) To declare two things to be similar in some respect ["to compare X to Y"].
  "Astronomers have compared comets to dirty snowballs."
• (transitive, grammar) To form the three degrees of comparison of (an adjective).
  "We compare "good" as "good", "better", "best"."
• (intransitive) To be similar (often used in the negative).
  "A sapling and a fully-grown oak tree do not compare."

noun

• (uncountable) Comparison.
  "His mighty Champion, ſtrong above compare,"
• (countable, programming) An instruction or command that compares two values or states.
  "[…] including addition and subtraction, memory operations, compares, shifts, logic operations, and condition operations."
• (uncountable, obsolete) Illustration by comparison; simile.
  "Rhymes full of protest, of oath, and big compare."