it v-link ADJ for n to-inf
The 'normal' and 'rare' group
These adjectives indicate that an event or situation is common or uncommon. The event or situation is indicated by the prepositional phrase beginning with for and the to-infinitive clause.
common commonplace customary extraordinary natural normal rare routine standard traditional typical uncommon unprecedented unusual usual
Between the ages of three and seven, it's normal for children to complain of unusual aches and pains, because they know it gets adult attention very quickly.
All these near misses may sound worrying, but it is extremely rare for asteroids to collide with planets.
In ancient warfare it was routine for the victors to slaughter the retreating enemy.
It was unusual for there to be no problems.