1 point of Adaptive Force provides 0.6 bonus AD or 1 AP.
If the attack damage and the ability power of the unit are equal, the stat granted depends on the champion.
In most cases, the League of Legends Wiki omits adaptive force in favour of displaying the amount of AD or AP granted.
Attack damage and ability power gained from abilities, including those on items like, do not contribute towards determining whether attack damage or ability power is gained with adaptive force. For example, if a champion like has a fully stacked , 100 stacks of , and no other items, his adaptive force will be given as ability power. If he buys a , it will instead be given as attack damage, despite having considerably more ability power.
Sources of adaptive force bonuses
A similar effect can be found on:
Adaptive Damage: Deals either physical or magic damage depending on your bonus statistics, defaulting based on the origin of the effect.
If the attack damage and the ability power of the unit are equal, the damage determined depends on the champion.
Sources of adaptive damage