 As is common when dealing with formal languages that have grouping symbols (the left and right parenthesis, in our case), some parentheses will be omitted when it is safe to do so (that is, when they can be reintroduced in only one sensible way). Juxtaposing more than two \(\lambda\)-terms is, strictly speaking, illegal. To avoid the tedium of always writing all needed parentheses, we adopt the following convention: