As described in section Phonetic structure, Finnish has short and long vowels and single and double consonants. Normally, a long vowel is written with two identical vowel letters like aa, and a double consonant is written with two identical consonant letters like kk.
In loanwords, the spelling may differ from the pronunciation both in vowel length and in consonant doubling. This is described in section New loanwords.
In pronunciation information in Finnish dictionaries and other reference works, there are three common ways to indicate vowel length in foreign (and occasionally even Finnish) words: doubling as in normal writing, e.g. eaux [oo]; a colon after the vowel, e.g. eaux [o:]; and a macron (short horizontal line) above the vowel, e.g. eaux [ō].