Final answer:
The word 'always' in the given phrase is an Adverb, more specifically an adverb of frequency, providing information about how often something occurs.
Step-by-step explanation:
In the phrase, 'I always am happy when it is my birthday', the word 'always' is functioning as an Adverb. In grammar, adverbs are used to modify verbs, adjectives, or other adverbs.
More specifically, 'always' is an adverb of frequency, which tells us how often something happens or is the case. Other examples of adverbs of frequency include words like: often, sometimes, rarely, and never.
Learn more about Adverb