As in the other Western Romance languages, the main plural expression is the suffix -s, which may create morphological alternations similar to the ones found in gender inflection, albeit more rarely. The most important one is the addition of -o- before certain consonant groups, a phonetic phenomenon that does not affect feminine forms: el pols/els polsos ("the pulse"/"the pulses") vs. la pols/les pols ("the dust"/"the dusts").
If it is possible to answer this question, answer it for me (else, reply "unanswerable"): What is the usual way to make a plural?
suffix -s