Ortho, meta and para

1. Ortho (or 1, 2-) : if the two substituents are on the adjacent carbon atoms, the compound is said to be ortho (or 1, 2-).

2. Meta (or 1, 3-) : if the two substituents are on alternate carbon atoms, the compound is said to be meta or (1, 3-).

3. Para (or 1, 4-) : if the two substituents are on diagonally situated carbon atoms, the ompound is said to be para or (1, 4-).

Ortho, meta and para are generally displayed as o-, m- and p- correspondingly.