This is a very concise introduction. There is a much more comprehensive e-book, by the same author: Introduction to Finnish.
The Finnish language, spoken mainly in Finland but also by people of Finnish origin in Sweden and other countries, belongs to the Fenno-Ugric group of languages, which is a part of the Uralian family of languages. Other Uralian languages include: Estonian, which is rather near to Finnish; Hungarian, which is very different from Finnish, with a fairly small number of related words; and several languages spoken in Russia, mostly by small ethnic groups.
The Uralian family of languages is possibly related to Indo-European languages (such as English, German, Swedish, Latin, Russian, Hindi, etc), but the relationship is highly debatable. The arguments are based on a few similarities which might, according to other scholars, be based on language universals, loanwords, or pure coincidences. – Note that some similarities in vocabularies are caused by relatively new loanwords which were taken into Finnish from Swedish due to strong cultural contacts (only very few words have gone in the opposite direction).
There are several structural similarities between Uralian and Altaic languages. However, linguists generally do not regard the undeniable typological similarities as evidence for common origin. See the Finno-Ugrian FAQ, section Language relationship, and sci.lang FAQ, section How are present-day languages related?
Both Uralian and Indo-European protolanguages had a relatively rich system of word flexion, e.g. about six cases for nouns. Typically Indo-European languages have developed towards a more analytic system where grammatical relations are expressed by word order, prepositions, and other auxiliary words rather than word flexion. On the other hand, in Uralian languages flexion has typically been preserved, and in part it has even expanded. Thus, for example, contemporary English has essentially just two cases (nominative and genitive), whereas Finnish has more than a dozen cases. Finnish has also a rich set of verb forms.
Thus, Finnish is a synthetic language: it uses suffixes to express grammatical relations and also to derive new words. To take a simple example, the single Finnish word talossanikin corresponds to the English phrase in my house, too. The suffix -ssa is the ending of the so-called inessive case, roughly corresponding to the English preposition in. The suffix -ni is a possessive one, corresponding to my in English. And the suffix -kin is an enclitic particle corresponding to the English word too (and the Latin enclitic -que). An example of verb flexion is kirjoitettuasi, which requires an entire sentence when translated into English: after you had written.
There are, however, some tendencies from synthetic to analytic expression in contemporary spoken Finnish. Thus, in free speech most Finns would rather say e.g. mun talossa (with mun corresponding to English my) than talossani, and verb forms like kirjoitettuasi usually only appear in written language – spoken language uses an analytic expression roughly corresponding to the English one.
Flexion uses suffixes only in Finnish. Originally the system was simply agglutinative: suffixes were “glued” to words by simple concatenation. (Compare this with e.g. the old Indo-European system of vowel alteration, which still lives in irregular verb flexion like in English sing : sang : sung.) However, due to various phonetic changes, in Finnish suffixes very often cause changes in the word root, causing phenomena which resemble flexion (e.g. juon ‘I drink’, join ‘I drank’), and for several suffixes there are alternative forms. Typical changes in the base word include:
For several suffixes, there are two alternative forms, because Finnish (unlike e.g. Estonian) has a phonetic feature called vowel harmony: in a non-compound word, the back vowels a, o, u do not appear in a word which contains any of the front vowels ä, ö or y, and vice versa. (Vowels e and i are neutral with respect to vowel harmony.) Thus e.g. the so-called inessive case suffix has two forms, -ssa and -ssä, so that e.g. the word kala takes the first form and kylä takes the second.
Suffixes are also used for word derivation. Another word formation tool is composition: glueing two words together. The following list of derived and composite words should give some idea of the mechanisms:
The word derivation tools have been used to produce names from Finnish ingredients instead of borrowing international words. For example, telephone is puhelin and university is yliopisto in Finnish. This approach was especially used in the 19th century when Finnish was consciously developed from the status of a language spoken by common people into a written, official (since 1863) and cultural language. Later international words have been adopted to a greater extent, so e.g. television is televisio in Finnish, but word formation has still been used e.g. for words like tietokone ‘computer’.
However, Finnish has quite a lot of loanwords from several Indo-European (and other) languages, adopted during a long period of time. However, especially old loanwords are difficult to recognize, partly because they have been taken from the predecessors of contemporary languages, partly because they have been adapted to fit into the Finnish phonetic system.
Truly Finnish words – i.e. excluding newest loanwords – obey the following phonetic rules:
In spoken Finnish, final vowels of some words are often dropped out, which leads to forms not complying with the above-mentioned rules. E.g. kaksi ‘two’ often becomes kaks.
This means that loanwords may have undergone quite considerable changes. However, apart from these phonetic adaptations, Finnish tends to be a conservative language in the sense that words change very slowly. For example, linguists think that the Finnish word kala ‘fish’ is exactly the same as in the proto-Uralian language thousands of years ago, and the Finnish word kuningas borrowed from Germanic languages has remained almost unchanged through centuries whereas in the Germanic languages the word has changed quite a lot (English king, Swedish kung, German König etc).
You have probably now realized why Finnish words are rather long in the average: root words are long due to the conservativeness, suffixes and composition are used to derive new words, and suffixes are used for flexion.
The phonetic rules mentioned above make the language easy to pronounce in a sense. However, there are several difficulties if you try to learn Finnish and your native language is English, for example. Some vowel sounds, especially those denoted by “y” (corresponds to German “ü”) and “ö”, take some time to learn. The diphthongs such as “uo” (in e.g. “Suomi” ‘Finland’) might take even more time. Additional difficulties are caused by double consonants such as “kk”, which should be pronounced basically as prolonged consonants. The difference between single and double consonants is very often distinctive; e.g., laki and lakki are completely different words, in pronunciation and meaning. Similarly, the length of vowels is distinctive two, and a long vowel is (almost) always written by doubling the vowel letter, e.g. “aa”.
On the positive side, the Finnish pronunciation rules are rather regular. It has even been claimed to be perfectly regular so that each letter always means one and the same sound and vice versa, but this is not quite true.
Word order is often said to be “free” in Finnish. The truth is that one can often change word order without changing the basic meaning of the sentence, but the emphasis or side meanings or style typically changes. Consider first the English sentence Pete loves Anna. If we change the word order to Anna loves Pete, we get a sentence with an entirely different meaning. Not so in Finnish: Pete rakastaa Annaa and Annaa rakastaa Pete both have the same basic meaning in the sense of speaking about Pete loving Anna. The case suffix -a in Annaa designates the grammatical object, no matter what the word order is. (If we wanted to say that Anna loves Pete, we would say Anna rakastaa Peteä.) In fact, in this case we could put the words of this sentence into any order, still speaking about Pete loving Anna, but with different purposes and different tones:
Some specific grammatical features of Finnish: