Incorrect spelling, explanation: we do not double the last consonant of the word here, because it ends with two vowels and the consonant – there is no need to double the n at the ends. This is why trainning is the wrong form. The correct spelling is training.

Correct spelling, explanation: this word is a noun made by adding suffix -ing to word train. As the word ends with two vowels and the consonant, the consonant is not doubled, therefore training is the correct form. Trainning is a misspelling here.

Definition of training:
noun, a certain time to train, physically or in another way
Tomorrow we have marketing training, I think it will be very interesting.
I’m sorry I have to go now, or else I’m late for my karate training.

Incorrect spelling

Incorrect spelling

Incorrect spelling

Incorrect spelling