Ordinary referential it has some referent. As a result, it can be replaced by a more complex description of that referent, and it can function (though marginally) as a sentence fragment answer to a question. Referential it can also (marginally) receive stress.
| (1) | a. | It bit the zebu. | |
| b. | The tsetse fly bit the zebu. | ||
| (2) | a. | What bit the zebu? | |
| b. | ? | (pointing) It. |
Expletive it doesn't refer, so it can't be replaced, as shown in (3), and even the question (4a) that the sentence fragment (4b) attempts to answer is ungrammatical. In contrast to referential it, expletive it can never receive stress.
| (3) | a. | It seems that the manuscript has been found. | |
| b. | * | The fact seems that the manuscript has been found. | |
| (4) | a. | * | What seems that the manuscript has been found? |
| b. | * | It. |
Ordinary adverbial there has a locative meaning, so that the adjuncts (right) here and (over) there render (5a) and (5b) contradictory and redundant, respectively. It is possible to stress ordinary there.
| (5) | a. | # | There comes the train (right) here. |
| b. | There comes the train (over) there. |
Expletive there, on the other hand, has no such locative meaning, and so both sentences in (6) are completely acceptable. In contrast to ordinary there, expletive there can never receive stress.
| (6) | a. | There is a clean shirt (right) here. | |
| b. | There is a clean shirt (over) there. |