You can change the meaning of most adjectives by adding a prefix that means not: un-, im-, in-, ir-.
For example, the word unimportant means not important and the word inactive means not active.
Examples:
| un- | im- |
in- | ir- |
| uncomfortable unprofitable unwise unimportant unhelpful unsuccessful unhealthy | immobile impermanent impossible immature | inconvenient incomplete inactive inexperienced independent | irregular irreplaceable irresponsible |