The Shulchan Aruch (EH 172) lists the features which defines someone as a "Seris." We must distinguish between (1) a "Seris Chamah" (literally, a "Seris of the sun"), or a person who was born as a Seris and therefore was a Seris from the moment that he "saw the sun," and (2) a "Seris Adam," who was rendered a Seris by the hands of man.

1. The Shulchan Aruch (EH 172:5) states that the distingushing features of a Seris Chamah are as follows:

(a) he does not possess a beard,

(b) his hair is soft (see Be'er ha'Golah, letter "Kaf"),

(c) his skin is smooth,

(d) when he urinates, the water does not form an arch,

(e) his Zera is clear and watery (Rashi to Yevamos 80b, DH Docheh),

(f) his urine does not stench when left in a vessel for a period of time (Rashi to Yevamos 80b, DH Machmitzin),

(g) when he takes a bath in the cold weather, his skin does not let off steam, and

(h) his voice is similar to that of a female.

2. The Rema writes that hairs are the most important feature. If he has 2 hairs in his beard, he is considered a Seris only if he possesses all of the above features. On the other hand, if he does not possess 2 hairs in his beard, then he is classified as a Seris even if he possesses only one of the above features. In addition, if he has 2 hairs elsewhere on the body, this determines that he is not a Seris even if he possesses all of the above features.

3. Now, to the definition of a Seris Adam: The Shulchan Aruch (EH 172:7) states that if his Ever or testacles have been cut, deatched, or crushed, he is considered a Seris Adam.

Kol Tuv,

Dovid Bloom