"My sister went out with a long jumper". Here's a claim with two meanings, and reading it, you'd never be sure which was intended. But hearing it would clarify things, because the speaker has a way of communicating the intended meaning. It's the vocal effort known as 'stress'. "Long jumper" (athlete) is two words acting as a single lexical item. A single lexical item has only one stress: O oo. "Long jumper" (garment) is two lexical items - adj +noun, so two stresses: O Oo. So here's an example of what we might call, a 'stress minimal pair'. Stress doesn't usually make such an obvious contribution to distinguishing between meanings, so examples like this can be useful in illustrating the purpose of stress. In my next class, I'm going to put the sentence on the board and ask students to explain it, and see how much of the above can be elicited, and how the students themselves choose to express the concepts. Incidently, the characters in the example sentence are purely ficticious and any resemblance to actually existing people is nothing more than coincidence.
(Picture/example taken from PronPack 3)