únicamente
/ˌunikaˈmente/ · B2 · adv
only, uniquely
☝️ única + mente = one-only + manner: in a one-and-only way
Built from the adjective única (sole, unique) plus the adverb suffix -mente, like English -ly. So únicamente is literally 'uniquely', and it means 'only' or 'solely'. Spot única inside it and you can recall the meaning.