Correct spelling, explanation: the root of the word humorous is the noun humor. It is worth noticing that the word humor can also be spelled as humour. However, the only correct spelling of an adjective is humorous. The word entered English from Latin, in which it had the form humere and used to mean humid. Later, the meaning of the word humorous evolved, and finally, it changed to the one we know today.

Definition of humorous:
1. adjective – funny, making you smile and laugh;
The story of his first job interview was so humorous that everybody laughed at it for weeks.

Phrases with humorous:
Some common phrases with humorous include: extremely humorous, mildly humorous, delightfully humorous;
One of the handed in such an extremely humorous story that the teacher couldn’t believe he wrote it on his own.
It was a mildly humorous novel, which was a pure pleasure to read during the holiday.
The movie is delightfully humorous and even small kids can watch it.

Incorrect spelling, explanation: as in English, the word humor can also be written as humorous, many users of English wrongly assume that the same rule applies to the adjective humorous, which they misspell as humourous. This form, however, is not acceptable.

Incorrect spelling