The length of phoneme is important in Finnish, because it has distinctive function. For example : tuli - tuuli - tulli. (fire, wind, customs.)
One side of this phenomenon is the consonant gradiation, wich means that length of plosives (k, p, t) vary.
| Strong grade | Weak grade |
| kk/pp/tt | k/p/t |
| kukka pappi matto |
kukan papin maton |
| k/p/t | -/v/d |
| käki käpy koti |
käen kävyn kodin |
| Strong grade | Weak grade |
| mp | mm |
| lampi | lammen |
| nt/lt/rt | nn/ll/rr |
| santa lanta ranta |
sannan lannan rannan |
| nk | ng |
| kenkä | kengän |
| k | v |
| suku | suvun |
| lke/rke/hke | lje/rje/hje |
| kärki | kärjen |
Basic rule: strong grade is used in the syllable is open (ends with vowel), weak grade when syllable is closed (ends with consonant). Usually this means, that when you add an ending wich closes the syllable (for example genetive -n) you must use weak grade.