Frequency: The word is one of the 3000 most common words in English.
1.
Allied forces or troops are armies from different countries who are fighting on the same side in a war.
...the approaching Allied forces...
ADJ: ADJ n
2.
Allied countries, troops, or political parties are united by a political or military agreement.
...forces from three ~ nations.
ADJ: ADJ n, v-link ADJ to n
3.
If one thing or group is ~ to another, it is related to it because the two things have particular qualities or characteristics in common.
...lectures on subjects ~ to health, beauty and fitness...
= associated
ADJ: v-link ADJ to/with n, ADJ n
4.
Something that is ~ to another thing occurs with the other thing. (FORMAL)
He possessed a raw energy ~ to a feeling of something special.
...a disastrous rise in interest rates ~ with a stock market slump.
= coupled
ADJ: v-link ADJ to/with n