In his previous volumes in this series, D. Geraint Lewis - author of an impressive range of popular books for Welsh learners - has cast light on the mysteries of Welsh mutations, verbs, adjectives, prepositions and numerals. In this new book, he tackles adverbs, the extensive list of adverbial phrases included here showing their importance. As Welsh often uses other parts of speech to fulfill adverbial functions (cartref: home; gartref: at home), he looks at the use of mutation to indicate that the word is functioning adverbially, those adverbs that do not mutate, the dual nature of these words, and the use of yn and the functions (including an adverbial one) it can perform in a sentence. An essential reference guide for both advanced learners and native speakers who would like to get to grips properly with this complex area of Welsh grammar.