In Welsh grammar, the Adverbs Theory refers to the study of how adverbs function within a sentence. Adverbs play a crucial role in providing additional information about verbs, adjectives, or other adverbs.

In Welsh, adverbs can be formed in several ways. Some adverbs are derived from adjectives by adding the suffix -ion, such as “araf” (slow) becoming “arafion” (slowly). Others are formed by adding the suffix -aeth to verb stems, like “cerdded” (to walk) becoming “cerddedol” (walkingly).

Adverbs in Welsh can also be formed by using certain structures. For example, the adverb “yn aml” (often) is formed by combining the preposition “yn” with the adjective “aml” (many).

Adverbs in Welsh can also be placed in different positions within a sentence. While the most common position is after the verb or adjective, they can also be placed at the beginning or end of a sentence to emphasize the adverbial meaning.

Overall, understanding the Adverbs Theory in Welsh grammar is essential for constructing sentences accurately and effectively in the Welsh language.