Two different words that have the same meaning are known as:

Words that have the same or similar meanings are called synonyms. This term comes from the Greek roots "syn," meaning together, and "onym," meaning name. Synonyms are useful in enriching language, allowing speakers and writers to express similar ideas in various ways, thereby avoiding repetition and adding nuance to communication.

For example, the words "happy" and "joyful" are synonyms because they convey similar feelings. Understanding synonyms is crucial in reading comprehension and vocabulary development, as they allow for a broader range of expression.

The other terms relate to different linguistic concepts. Similes are figures of speech that compare two different things using "like" or "as." Antonyms refer to words that have opposite meanings. Hyponyms are more specific terms within a broader category; for example, "rose" is a hyponym of "flower."