Incorrect spelling, explanation: to create an abstact noun describing condition we can add suffix -th to an adjective. This way we transform long into length. The word comes from Old English lengthu. This is why lenght is the wrong spelling, and the correct one is length.

Correct spelling, explanation: length is the correct form of this noun. It originates from adjective long with suffix -th, which creates abstract nouns to express quality. In Old English: lengthu, then the word transformed into today’s form length. This is also why lenght is incorrect.

Definition of length:
noun, measure of time or space; the longest extent
Can you tell me what is the length of the mattress you need?
Length of lectures at this university is usually 90 minutes.

Idioms and expressions with length:
at length, fully, thoroughly; at last:
We discussed the problem at length and came to the conclusion.
to go to any lengths, when someone is very desperate and wants to achieve something no matter how extreme their methods are:
He would go to any lengths to win this race.
at arm’s length, to keep at bay or to be very close to a person (so you can reach it with your arm straight):
I don’t trust him so I keep him at arm’s length.
Just in case, the nurse is always at your arm’s length.

Incorrect spelling

Incorrect spelling

Incorrect spelling

Incorrect spelling