Yes, and the inventor of the language eventually removed ELSE from his dialects, amusingly. These days he says that his code has very few conditional statements.

I think the tactic strategy to achieve this is to confine conditional branches in a few well chosen words.

For instance if you have a word SORT that sorts the top pair on the stack, which has to have a branch:

    : SORT 2DUP < IF SWAP THEN ;

then you can build "if-less" MIN, MAX and ABS:

    : MIN SORT NIP ;

    : MAX SORT DROP ;

    : ABS 0 SORT SWAP - ;

Yes. It is used in the sense of the English statement:

IF you go to the store get some butter THEN come right back.

So THEN is where the program continues on a false condition. Typically Forth. It uses an alternative way of looking at things.

Yes, Forth is stack-based RPN so "IF" naturally comes after the test; "THEN" marks the end of the block; so if you want "ELSE" it ends up in the middle to let you nest conditions.

    : /CHECK   DUP 0= IF  ." invalid " DROP  ELSE  /  THEN ;

https://www.forth.com/starting-forth/4-conditional-if-then-s...