The general principles of typography for Finnish are the same as those for other languages using the Latin alphabet. However, there are some specialties, described in this section.
Principles of typography, adapted to Finnish, are presented in Typografian käsikirja. Specialties of digital publishing are described in Verkkojulkaisun typografia.
The main issue in typesetting Finnish texts is usually the need for hyphenation due to long words. Without hyphenation, you often get disturbing variation in line length or, if justification is applied, disturbingly large gaps between words.
Finnish hyphenation rules are relatively simple. However, a typesetting program might lack support to Finnish hyphenation. Moreover, correct hyphenation of compound words can be difficult and may require manual checking and control. The techniques and problems are discussed in the next section, Hyphenation.
When selecting fonts for texts in Finnish, the most important language-dependent thing is to make sure that the rendering of ä and ö is acceptable. They should be manifestly different from a and o, so the dots must not be too small. On the other hand, the dots should be relatively close to the base letters and not excessively large; e.g., the Trebuchet MS font has ä and ö as too prominent to many people’s taste. In addition, letters š and ž should be available and acceptable.
Depending on content, other letters can be important, too, as explained in subsection A closer look at the use of letters in Finnish texts. In particular, if the text contains Swedish names, the letter å is important. This can be a problem, because the ring above is difficult to implement well in font design (e.g., the å in Verdana is rather grotesque).
The en dash “–” should be clearly wider than the hyphen “-”. In some fonts, they are of about equal width. The distinction is essential e.g. in book authorship notations: Virtanen-Lahtinen is one person with a double name, Virtanen–Lahtinen is two persons.
In the following contexts, the space should be non-breaking, i.e. text reflow should never cause the space to be turned to a line break:
In number notations, there are typographic reasons for making the space narrower than a normal space, e.g. using the thin space character, if possible.
Abbreviations of initials of names are followed by a space in Finnish, contrary to common English practice, e.g. B. Virtanen, J. K. Paasikivi. There is no formal recommendation on this, but on typographic grounds, such spaces should be non-breaking and could be thin.
The methods used to prevent inadequate line breaks vary by the tools of writing. Quite often, you can use the no-break space character instead of a normal space.
In date notations like 1.4.2015, no spaces should be used. Small added spacing after the periods is acceptable and is recommended by typographers.
The letters used in Finnish texts can be classified as follows, roughly in descending order by conventionality and familiarity:
The letters that are needed for writing purely and originally Finnish words: a, d, e, g, h, i, j, k, l, m, n, o, p, r, s, t, u, v, y, ä, ö. There is no acceptable way to dispense with ä and ö in Finnish texts. In particular, the convention (used in German for example) of replacing them by ae and oe is not acceptable for Finnish, although this replacement method is generally known by Finns due to its application in international texts.
Letters that appear often in (relatively new) loanwords: b, f.
Base letters that are conventionally regarded as part of the Finnish alphabet, yet appear only in words of foreign origin that have preserved their original spelling and, naturally, in foreign names, and derivations of such words: c, q, w, x, z, å.
The letters š and ž. They are officially regarded as part of Finnish orthography, although they occur relatively rarely and only in loanwords, foreign names, and their derivations and although they are often omitted when listing the Finnish alphabet. However, in newspapers, informal texts, and even in many books, these letters are very often replaced by the letter pairs sh and zh, respectively.
Letters that appear relatively often in names of foreign origin, their derivations, or loanwords that have been taken directly from another language (foreign words). This group is difficult to specify, but it is probably adequate to count at least the following letters:
é in names, including Swedish names used in Finland (e.g. Lindén), and also in foreign words like moiré.
á in names, including Swedish names used in Finland, though less often (e.g. Collán).
à in the French preposition à, which is sometimes used in Finnish to indicate a range or a unit price.
ü especially in names and foreign words of German (or Estonian) origin, including surnames used in Finland, like Schüler.
ñ in foreign (Spanish) words like mañana.
ç sometimes in foreign words like garçon.
ß in German names like Wilhelmstraße; very often replaced by ss.
ë in scientific names of organisms, though the dieresis is often omitted.
The letters æ and ø due to their frequency in Norwegian and Danish names. Often replaced by ä and ö, respectively.
The letter õ due to its appearance in Estonian names. Often confused with ö.
Other Latin letters that appear relatively often in names, but hardly in foreign words. The diacritics used in these letters are omitted far more often than for the previous group, and readers may fail to notify the diacritics. This group includes the following Latin letters: ã, í, ó, ú, ý, è, ì, ò, ù, â, ê, î, ô, û, ï, ÿ. (These are the letters with diacritic that belong to ISO Latin 1 and have not been listed above. Among these, those commonly used in French and Italian, such as è, are probably more widely used and recognized than the rest.)
The additional letters used in the Northern Sámi language: č, đ, ŋ, ŧ. They appear in personal, geographic, and company names in Northern Finland. Since they are often unavailable in fonts and difficult to produce on keyboards, it is common (but not correct) to use simple c, d, n, t instead.
The additional letters used in other Sámi languages spoken in Finland: ʒ (ezh), ǥ (g with stroke), ǧ (g with caron), ǩ (k with caron), ǯ (ezh with caron).
Letter ȟ (h with caron), which is used in the Romani language as spoken in Finland. It is rarely used, and fonts often lack it.
The letters ð and þ (used e.g. in Icelandic). They are classified as Latin letters and available in the Latin 1 repertoire, but not widely recognized in Finland. In Icelandic names, they are often replaced by d (or dh) and th, respectively.
Combinations of Latin letters a–z with diacritic marks not listed above, such as ć (c with acute, used e.g. in Croatian). In actual practice in Finland, these are very often written without the diacritic mark. These, and characters in the following classes, only appear in proper names and literal quotations. Among these characters, those that appear in official languages of the European Union (especially Polish, Lithuanian, and Latvian) can be expected to be, or to become, more common and widely recognized than the rest. The distinction drawn here between this group and the preceding group is largely based on technical considerations such as the widespread support to Latin 1 repertoire in software used in Finland.
Other letters classified as Latin letters in the broad sense, such as ə (used in Azeri).
Letters used in non-Latin writing systems, such as Cyrillic or Greek. These occur basically in scientific texts only, mostly in linguistics (in the rare cases when transliteration or transcription is not used) and in mathematical and scientific notations. The only such letters in common use are the capital omega Ω, used as the ohm symbol, and the small mu μ, used as micro prefix in the international system of units. However, the first few lowercase letters of the Greek alphabet, α, β, γ etc., might be seen even in newspaper texts (in astronomical, chemical, and other terms, e.g. α-tokoferoli = alfatokoferoli).