When you say the word [NOSTRIL], you pronounce the [NOS] slightly louder, at a slightly higher pitch, and for a slightly longer duration than when you pronounce the [tril]. The first syllable [NOS] is STRESSED, and the second syllable [tril] is UNstressed.

Oronyms can illustrate the difference between STRESSED and UNstressed syllables. The two oronyms on the right include exactly the same sounds in the same order, but the stress is on different syllables.