The spoken language has mostly developed naturally from earlier forms of Finnish, and spread from main cultural and political centers. The standard language, however, has always been a consciously constructed medium for literature. It preserves grammatical patterns that have mostly vanished from the colloquial varieties and, as its main application is writing, it features complex syntactic patterns that are not easy to handle when used in speech. The spoken language develops significantly faster, and the grammatical and phonological simplifications include also the most common pronouns and suffixes, which sum up to frequent but modest differences. Some sound changes have been left out of the formal language, such as the regularization of some common verbs by assimilation, e.g. tule- → tuu- (although tule can be used in spoken language as well).
Written language certainly still exerts a considerable influence upon the spoken word, because illiteracy is nonexistent and many Finns are avid readers. In fact, it is still not entirely uncommon to meet people who “talk book-ish” (puhuvat kirjakieltä); it may have a connotation of pedantry, exaggeration, moderation, weaseling or sarcasm. More common is the intrusion of typically literary constructions into a colloquial discourse, as a kind of quote from written Finnish. It should also be noted that it is quite common to hear book-like and polished speech on radio or TV, and the constant exposure to such language tends to lead to the adoption of such constructions even in everyday language.
A prominent example of the effect of the standard language is the development of the consonant gradation form /ts : ts/ as in metsä : metsän, as this pattern was originally (1940) found natively only in the dialects of southern Karelian isthmus and Ingria. In fact, it has arisen from the spelling ‘ts’ for the dental fricative [θː], which has disappeared. In spoken language, a fusion of Western /tt : tt/ (mettä : mettän) and Eastern /ht : t/ (mehtä : metän) has been created: /tt : t/ (mettä : metän). It is notable that neither of these forms are identifiable as, or originate from, a specific dialect.
The orthography of the informal language follows that of the formal language. However, sometimes sandhi may be transcribed, especially the internal ones, e.g. menenpä → menempä. This never takes place in formal language.