The Partitive Plural (-ita / -itä)
Use the -ita and -itä endings to form the partitive plural for certain longer words and vowel combinations. You will use these often when requesting indefinite amounts of hotel amenities, or stating that something is missing with the verb puuttua (to be missing).
For words ending in -e, like pyyhe (towel) and esite (brochure), the stem ends in -ee-. Drop one -e- and add -itä to form -eitä (note that pyyhe also undergoes consonant gradation to become pyyhkeitä).
Longer Words and Vowel Changes
For many words with three or more syllables ending in -a, the final vowel changes to -o- before adding the -ita ending. For example, saippua (soap) becomes saippuoita.
Adjectives ending in -eä, like pehmeä (soft), simply drop the final -ä before adding -itä (pehmeitä). Combine this with a longer word like lakana (sheet), which becomes lakanoita.
The same -oita rule applies to words ending in -ia, such as astia (dish) and pistorasia (socket). The final -a changes to -o-, resulting in -ioita.
Bringing It Together
Professional titles with three or more syllables, like virkailija (clerk), also follow the -a to -oita rule.
Remember that adjectives and nouns must agree. Notice how pehmeä and the -e word lisävuode (extra bed) match in the partitive plural (pehmeitä lisävuoteita), and how different words take their respective plural endings when listed together.