Céline Dionin konsertit lisäävät lentojen kysyntää.

0. Céline Dionin konsertit lisäävät lentojen kysyntää.

The verb 'lisätä' takes a partitive object, so you use 'kysyntää' instead of 'kysyntä'. You use the partitive case here because the action is ongoing and the object is not fully completed. Whenever you use verbs indicating partial effect or ongoing action, always put the object in the partitive.

1. Lentohakuja on 11 prosenttia enemmän kuin viime vuonna.

The partitive plural is required after words indicating quantity or comparison, like 'Lentohakuja' with 'enemmän'. When you express an unspecified amount or use comparatives, the noun must take the partitive plural ending '-ia/-iä' or '-a/-ä'. You apply this rule to any noun, for example, 'paljon vettä' (a lot of water) or 'enemmän aikaa' (more time).

3. Dionilla on 16 konserttia syyskuussa ja lokakuussa.

The adessive case ending '-lla' combined with 'olla' expresses possession, like 'Dionilla on'. Instead of a verb meaning 'to have', you use the structure '[Person]-lla on [Thing]' to show ownership. You can apply this to say you have something, for example, 'Minulla on auto' (I have a car).

4. Hän laulaa sekä ranskaksi että englanniksi.

The translative case ending '-ksi' expresses the language someone speaks or sings in, like 'ranskaksi'. This case shows a change of state or the role something takes, which in this context means 'in the form of French'. You can use this same structure for any language, such as 'suomeksi' (in Finnish) or 'saksaksi' (in German).

5. Aasiaan matkustaminen on lisääntynyt paljon.

The perfect tense formed with 'on' and the past participle describes past actions that affect the present, like 'on lisääntynyt'. You form this by combining the verb 'olla' with the verb's '-nut/-nyt' stem, which changes to '-ne-' before the personal ending. You use this whenever you want to say something 'has increased' or 'has happened' recently.