Hi Refreshed,
In reviewing my notes in looking up the answer to your question, I have discovered I have made a small mistake in my previous information (which I will clear up here, but the overall point is still true).
The root ("stem") word "diakon-" (pronounced dee-a-kon), means "deacon". Depending on what suffix is appended *and* which article is placed after the noun, we can determine the gender (masculine, feminine, neuter), number (singular, plural) and case (nominative, genitive, etc.).
In the case of "diakon(o)-", the endings can be -os (usually for masculine) or -on (for feminine and neuter). When we are trying to determine gender specifically, the article "a" or "the" gives the answer. In Rom 16:1, is says Phoebe is "diakonon ths": the noun is non-masculine, and the article is feminine. Thus she was a female "diakon-". I don't know of anywhere in scripture where "diakon-" is used in a neuter form, but in a form similar to Rom 16:1, it would say "diakonon tou" (intead of "ths").
Also, and I don't think this has been mentioned yet in this thread, Phoebe wasn't just a general "servant" because the Greek word for a servant in general is "doulos" (or doulon in non-masculine). Deacons were servants, but a specific type of servant - a specific role/office in the church. Phoebe was a "diakonon" of the church, not a "doulon" of the church.