Within a word, a hyphen (-) may appear between the parts of a compound word, as in English, but with more complicated rules for its use, described in section Hyphens in compounds. For example, a hyphen is used when the first part ends with a vowel and the second part starts with the same vowel, e.g. kuorma-auto (truck). A hyphen may also appear at the start of a word, representing an omitted first part of a closed compound. For example, syntymäaika ja -paikka is short for syntymäaika ja syntymäpaikka, and maa- ja metsätalous is short for maatalous ja metsätalous. Thus, a hyphen at the start of a word indicates that the word is the second part of a compound, with two or more preceding words constitutins the first part of the compound.
The hyphen should be kept as separate from the en dash (–). When mistakes are made with this, usually the hyphen is used instead of the en dash. However, when writing with Microsoft Word, the default settings have caused a word-initial hyphen to turn to an en dash. Incorrect written forms like syntymäaika ja –paikka have therefore been very common. The bug has been fixed in new versions of Word.
An apostrophe (’) is used inside words for a few purposes:
In inflection, an apostrophe is used if the spelling of a foreign word ends with a consonant but the pronunciation ends with a vowel, as in show [šou]. Additional examples: Bordeaux [bordoo] : Bordeaux’n [bordoon], Kaj [kai] : Kaj’lla [kailla]. Mistakes are often made with this, either by omitting the apostrophe when it is required or by using it in words of other types.
However, an apostrophe is in principle permitted whenever it is necessary to indicate the base form of the word. You might use it e.g. in the word form Sinise’n to indicate that it is the genitive of the foreign name Sinise and not a regular genitive of the Finnish word Sininen. Tthis is rare; usually the basic form of the name is obvious enough from the context or otherwise.
The correct apostrophe character is curly (’), as in English, but a vertical apostrophe (') is very common, as in English, since it is easier to type.
When a suffix is added to a word that is written using digits or special symbols or an abbreviation, the suffix is preceded by a colon “:”. Thus, we can write kolmessa as 3:ssa (the digit stands for the stem of the numeral, kolme) and ulkoministeriössä (in the Foreign Office) as UM:ssä (the abbreviation UM stands for the base form ulkoministeriö). If an abbreviation is read as a word and not as spelled out or by pronouncing the names of letters, no colon should be used. Thus, “in NATO” is written as NATOssa or Natossa.
When the colon is used that way, it is followed by the suffix only. This is difficult even to native speakers, since it requires a grammatical analysis of the word rather than just naturally learned inflection of words. Therefore, mistakes are very common in this area. Native speakers may even have greater difficulties than people who have learned Finnish as a foreign language on a more theoretical basis. For example, to write the word kymmenenteen using digits, you need to recognize that the word has the ordinal number suffix nte- and the illative suffix -en, so that you need to write 10:nteen. The digits 10 here represent the inflectional stem kymmene-.
A binding vowel i that appears in the full form of a word is omitted when the word is written using an abbreviation or symbol. For example, if the symbol Å is used for the outdated unit ångström and the genitive form ångströmin is needed, it is written “Å:n”, not “Å:in”.
Further complications are caused by the additional rule that if a suffix starts with a vowel that is pronounced as part of a long vowel, the long vowel is written in full, with two letters. For example, ulkoministeriöön would be written as UM:öön, if UM is meant to be read as ulkoministeriö, and as UM:ään (pronounced uu ämmään), if UM is read by letters, uu ämmä or uu äm.