Correct spelling, explanation: threat is a commonly used noun, which has a long history as it could already be found in Old English. Back then threat had the meaning of oppression. The word also appeared in Dutch and German languages, but it looked different and it had a different meaning. Today, threat is used in both written and spoken English.

Definition of threat:
1. noun – a suggestion that something bad will happen if some request or order isn’t followed,
He drinks and drives, which makes him a serious threat to other, innocent road users.

Collocations with threat:
Some popular collocations with threat are: under threat, pose a threat, and regard something as a threat.
Many animal species are under threat of extinction and need to be protected by environmentalists.
Access to alcohol at almost every shop poses a threat to children and teenagers.
Most teenagers don’t regard playing computer games as a threat when in fact, it has a great impact on their brains.

Incorrect spelling, explanation: threat is a word with a rather simple spelling and pronunciation, but a number of English users make a mistake and they spell the word as threath, with the -h letter at the end of the word, which is wrong. They probably associate threat with other similar words, such as breath. Nevertheless, the only correct spelling is threat.