Learn Dutch: Goede theorieën prikkelen de creativiteit. - Good theories stimulate creativity.

It comes down to word stress. Because the stress in the singular word theorie falls on the final syllable (-rie), you add the full suffix -ën to make it plural. If the stress fell on an earlier syllable (like in porie or bacterie), you would only add an -n and put the trema on the existing e (forming poriën and bacteriën).

What exactly does prikkelen mean here? Is it only used for abstract things like creativity?

Prikkelen means "to stimulate" or "to arouse" here, but its literal meaning is "to prick", "to sting", or "to tickle". You can use it physically—for example, a prickly sweater, carbonated water, or a sharp scent can all prikkelen. In a figurative sense, it is commonly used with the senses (de zintuigen prikkelen) or the imagination (de fantasie prikkelen).

Why is there a de before creativiteit? The English translation just says "creativity".

In Dutch, abstract nouns representing a general concept (like creativity, nature, love, or time) often take a definite article, whereas English usually leaves it out. While you could technically drop de in this sentence, keeping it sounds much more natural and idiomatic when making a broad statement about a concept.

Just as a quick refresher, why is it instead of ?