Increase ↔ Decrease
Increase
To become or make something larger in number or amount.
Prices increase before the festival season.
Decrease
To become or make something smaller in number or amount.
Traffic decreases on Sunday mornings in Chennai.
Remember: As verbs, stress the end: prices inCREASE. As nouns, stress the front: an INcrease. Don't say 'increase more'; increase already means 'more'.