In a sentence like Juoksin kilometrin (I ran a kilometer), the expression that specifies a quantity could be regarded as an object. Its case form is determined the same way as the case of an object, e.g. Juostaan kilometri (Let’s run a kilometer; 4th person, hence the nominative), En juossut kilometriä (I did not run a kilometer; negative sentence, hence the partitive), Juoksin useita kilometrejä (I ran several kilometers; indefinite plural, hence the partitive).
The quantifying expression can also specify time, e.g. Olin siellä viikon (I was there a week) or number of repetitions, e.g. Tapasimme kolme kertaa (We met three times). The words kerran (once) and paljon (a lot) are special in the sense that they are not used in the nominative; the genitive is used instead of it. Examples: Söin paljon (I ate a lot), Syötiin paljon (A lot was eaten), En syönyt paljoa (I did not each much).
Although the case rules for the object apply to these expressions, they are classified as adverbials of a special type in grammars. One reason to this is that they may appear along with a real grammatical object, e.g. Tapasimme hänet kolme kertaa (We met him/her three times), where hänet is the real object.
Normally an object-like quantifier expresses an amount of length, weight, money, time, or some other quantity, as in the preceding examples. Sometimes it expresses an amount less directly, as in Hän itki koko tanssin (He/she wept through the entire dance). However, it is more natural to make the expression more clearly quantifying, e.g. Hän itki koko tanssin ajan. Here the quantifier is koko tanssin aika, in the genitive form, where aika means “duration” rather than its most common meaning “time”.
An object-like quantifier may also indicate the amount of increase or decrease, as in Palkka nousi sata euroa (The salary increased by a hundred euros). The adessive, e.g. sadalla eurolla, is also used in such expressions. Language guides have often regarded such use of the adessive as foreign influence and recommended an object-like quantifier. However, the opinions have changed. The use of the adessive is even regarded as the only possibility or as the better option in some contexts, especially when the predicate expresses causation and it has a real object, e.g. Palkkaa nostettiin sadalla eurolla (The salary was raised by a hundred euros) is now preferred over … sata euroa.
The adessive is also regarded as more natural when the quantity is not a normal physical or monetary unit but is e.g. henki (person), työntekijä (worker), or paikka (position; place). It is the only possibility when no unit is expressed, just a number. Thus, Henkilökunta väheni sadalla hengellä (The staff decreased by a hundred people) is preferred over Henkilökunta väheni sata henkeä, and if the word hengellä is omitted, the adessive is the only possibility. The same applies when the expression relates to a -minen or -Us noun derived from a verb, e.g. henkilökunnan vähentäminen sadalla hengellä (decrease of staff by a hundred people).