To intensify the meaning of an adjective, we can use various adverbs. In English, the word “new” can be intensified by saying “brand new” or “really new”. In Finnish, we can similarly say aivan uusi or todella uusi. Alternatively, we can use an adjective-specific intensifier, often alliterating with the adjective and often written as a closed compound with it, e.g. upouusi. The word upo is used in this context only, so it is very specific to the adjective uusi.
There are also similar specific intensifiers for adverbs, such as yksin (alone): ypö yksin (all alone). An intensifier may also restrict the meaning of the modified word. As such, yksin can be used in neutral contexts like Hän teki sen yksin (He did it alone, by himself), but in such contexts, it cannot be intensified by ypö (but e.g. aivan yksin). When we say ypö yksin, it means being alone, without company, in a more or less negative sense.
The meaning a word-specific intensifier is that the adjective or adverb applies truely, genuinely, properly. When we say that a car is upouusi, it is more or less straight from the shop, as opposite to a car that has been used for a few weeks and could still be called uusi. Rather similar intensification can be achieved by reduplication, by using the adjective twice, the first occurrence being in the genitive, e.g. uuden uusi.
Usually each specific intensifier is used with one word only, and each adjective or adverb has at most one intensifier or a small set of similar intensifiers—more or less variants of the same word. The following list shows words with specific intensifiers (only the basic meaning of the adjective or adverb is given), ordered by the main word (in bold).
It can be seen that the intensifier typically looks like a word formed from the adjective via simplification and modification. It often consists of two syllables and looks like an adjective in base form. Alkusointusyntyiset vahvistussanat suomessa.
Some intensifiers look like inflected forms, though, e.g. apposen, which can be interpreted as the genitive of apponen. The word viti is actually an independent word, too (fresh snow), but hardly used in modern language that way. The word tuhka (ash) is a normal word, but its use as an intensifier seems to be independent of that.
The word sysimusta (jet-black) is not included in the list, since sysi (charcoal) has a few other uses. The compound can be interpreted as descriptive, “black like charcoal”, at least by origin, rather than having a special intensifier that has no meaning of its own. On similar grounds, the list excludes such interesting expressions like likomärkä (“soaking wet”), läpimätä (“through-rotten”), pikimusta (“pitch black”), raivoraitis (“ragingly sober”), rapajuoppo (“mud drunkard”), sikasiisti (“swine clean”), and umpihullu (“closed-mad”).
Most adjective-specific identifiers are written as the first part of a closed compound, whereas most adverb-specific identifiers are written as separate words. This tends to reflect the pronunciation, but there is variation in it as well as in writing; e.g. nonstandard forms like viho viimeinen and ypöyksin are relatively common.
New word-specific intensifiers are sometimes coined, though they mostly remain in limited, often jocular use, like rutiruotsalainen (really Swedish), more or less echoing supisuomalainen, and epoensimmäinen (the very first).