Incorrect spelling, explanation: this form is incorrect, because in this case suffix -th creates a noun of condition. There is such sound as ght in English, so probably this is the reason for the mistake, but the correct form is length. Just like other nouns of this type, length is the correct spelling.

Correct spelling, explanation: length is the correct form because it uses suffix -th, which creates nous describing quality or condition. Therefore lenght is a misspelling, and length, just like width or depth, is the correct form of this noun.

Definition of length:
noun, a measurement (usually of time or space) from one end to another in some more or less regular units or intervals – often measured in units such as inches, feet, or meters; the longest linear extent (measurement of something from end to end)
She measured the length of her hair every month to track its growth.
She checked the length of her dress before the big event to make sure it was the right length.
They measured the length of the room to determine how much paint they would need.
The length of the project is supposed to be maximum of 2 weeks.
What is the length of this pipe?
He checked the length of the rope to make sure it was sufficient for the task.

Phrases and idioms with of length:length:
There are many expressions with the word length, here’s a short list of the most popular ones:
→ arm’s length – the distance between one’s hand and elbow when the arm is extended straight out, used to describe maintaining a distance or avoiding intimacy with someone,
We always try to keep our business dealings at arm’s length to avoid any potential conflicts of interest.
→ at any length – to any degree or extent,
He’ll talk about the topic for hours if you let him, he’s very passionate about it and will go on at any length.
→ at arm’s length – at a distance where one can’t be easily reached or touched,
I don’t trust him so I keep him at arm’s length.
I try to keep my emotions at arm’s length when it comes to work, it helps me stay focused and professional.
→ cut to length – to trim or adjust to the desired size or length,
I had to cut the wood to length before using it to build the shelf.
→ cable length – the measurement of a cable, often expressed in feet or meters,
The cable length is too short, I need to get a longer one to reach the other side of the room.
→ full-length – the entire or complete length of something,
I watched the full-length movie, it was three hours long.
→ go to any lengths – to make great efforts or take extreme measures to do something,
I’ll go to any lengths to protect my family, I’ll do whatever it takes.
→ focal length – the distance from the center of a lens to the point where an image is in focus, used to describe the magnification or angle of view of a lens,
I need to adjust the focal length of the telescope to get a clearer view of the stars.

Incorrect spelling

Incorrect spelling

Incorrect spelling

Incorrect spelling