For example, in Greek (and a number of other languages) people say open or close a light instead of turn on and turn off. Thus a Greek learner may well say:
* I closed the light and went to sleep.
* an asterisk at the beginning of a sentence denotes it to be ungrammatical
What they have done here is use a Greek expression and simply converted it to English. This is an example of their MT influencing the TL.
* My hair are wet.
* The spaghetti are ready.
It is sometimes useful to have a working knowledge of the students' MT in order to be able to understand why certain mistakes are being made.