aika - melko - melkein

Aika means time, but it also means quite.

• Tämä harjoitus oli aika vaikea.  - This exercise was quite difficult. 
• Viime kerrasta on aika kauan aikaa. - It's been a while since the last time.

Another word for quite is melko, but I just realized that I never say it. I suppose it's a bit more formal than aika. 

• Olen melko tyytyväinen suoritukseesi. - I'm quite satisfied with your performance. 
• Käyn täällä melko usein. - I visit here rather often.

Notice that melko is very often mixed with melkein, which means almost. 

• Se oli melkein oikein! - That was almost correct!
• Mä melkein unohdin sen. - I almost forgot it.
• Mä oon melkein valmis. - I'm almost ready. 

Oh, you might also want to read my post about ihan.