Homographs are words which share the same spelling but are nevertheless different in meaning and possibly also in pronunciation. An example is the word ‘bank’, which can either refer to a financial establishment in which you can do a lot of things to your money, or an edge of a river. In this case, we say they are two different words which happen to share the same spelling and the same pronunciation.
There are also some closely related word pairs; in these pairs, the words share the same spelling (so they are homographs) but have different stress patterns. Take a look at the following list of such word pairs. If you observe carefully, a relationship between the stress patterns and the meanings of the words pops out immediately.
Apparently, if the stress (indicated in red) falls on the first syllable, it is the nominal form of the pair. If it falls on the second syllable, then it is the verbal form. The reason why this relationship exists is because these nouns are historically derived from their verbal counterparts by moving the stress to the first syllable.
What is noteworthy is that this tendency of nouns having initial stress is not unique to word pairs having both nominal and verbal forms. In fact, the majority of bisyllabic nouns have their stress on the initial syllable. Several examples are given below:
The next time you encounter a new bisyllabic noun, you know where to put your stress.