As a Noun:
1. The action of behaving in a way that is intended to make people believe that something is the case, although in fact it is not. English = pretence.
2. Something that is made to look like something real. English = imitation, copy.
3. An object, especially a work of art, which is made to appear real but which is not. English = fake.
As a Verb or Adjective:
1. To act in a way that is intended to make people believe that something is the case, although in fact it is not. English = pretend. Idiomatic English = make believe, put on an act.
2. To be made to look like something real; to be not natural and exist or happen only because people have created it. English = (be) artificial, (be) false, (be) fake.
3. Of a statement, idea or action, to not be true or to be based on wrong information. English = (be) false.
Interactive:
1. Used alone to mean that you will accept something as true or real, or try to do something that you doubt will work, only provisionally, as a kind of working hypothesis, in order to see what happens.
2. English = 'Okay, let's give it a go, then!', 'Let's see what happens then!', 'I'll try, but I don't think it will work!', 'Okay, let's assume it's the case', and so on.
As Modifier:
1. Used at the beginning of a sign sentence to mean that the action in that sentence is not real or actual, but you are going to pretend it is and see what that means. You know a past action did not happen, a current action is not happening,
2. or a future action has not happened yet, but you talk about it anyway. English = if.
3. 2. Used to introduce a possible situation or action. English = suppose, what if.