Head ache and Pain in the head

Head ache noun - Pain in the head caused by dilation of cerebral arteries or muscle contractions or a reaction to drugs.

Pain in the head and head ache are semantically related. In some cases you can use "Pain in the head" instead a noun phrase "Head ache".

Head ache and pain in the head are semantically related. Sometimes you can replace phrase "Head ache" with "Pain in the head", this phrases are similar.