Tractatus Logico Geneticus

Every mother is a woman.  Not every woman is a mother. Nobody who is not a woman is a mother.  

Every woman who is not a biological mother can act in the place of a biological mother.

Not every woman who is or acts as a mother is a good woman or a good mother.

The terms woman and biological woman are linguistically identical.

The phrase people who menstruate describes women who menstruate.  Not all women menstruate.  All people who menstruate are women.

Some syllogisms:

All mothers are women.  XX is a mother, therefore XX is a woman.  

All men are not mothers.  XY is a man, therefore XY is not a mother.

Almost all humans with XY chromosomes are men; rarely they are Swyer syndrome women; therefore no absolute conclusion can be generalized regarding XY genotype in the absence of phenotypical presentation of sex as a dyad.

Almost all humans with XX chromosomes are women; rarely they are de la Chapelle syndrome men; therefore no absolute conclusion can be generalized regarding XX genotype in the absence of phenotypical presentation of sex as a dyad.

All humans with XX (or X not-Y) chromosomes where an X is effectively absent, or sufficiently damaged to approximate a Y, are women suffering Turner syndrome.

All humans with XXX (trysomy) or XXY (Klinefelter syndrome) or XYY (Jacobs syndrome) or XYYY (XYYY syndrome - there is no identified 'YYY' or 'YY' syndrome) chromosomes are suffering atypical genetic expressions of sexual genotype (geno-atypical), some of whom may identify or be identified, currently, as intersex.

Intersex is always the product of genetic abnormality.

Abnormal is not a pejorative.

Hermaphrodite is a meaningful biological term, describing organisms capable of fulfilling both male and female reproductive functions.  With reference to humans it is an obsolete term, more precise but less desirable than intersex.

In cases if true hermaphroditism, the female reproductive function takes precedence.

Gender is a term specific to grammar, classifying pronouns (and in English, rarely, nouns -- eg, a ship as female). 

Gender is to grammar as genus is to taxonomy.  Genus is based on quantifiable genetic or cladistic distinguishers.

Gender is never a descriptor in biology. No vertebrate has a gender; all vertebrates have a sex.  Thus, man or woman are gendered linguistic terms for biologically male or female homo sapiens (ie,  humans or people).   

Gendered terms describing innate biological characteristics are artifacts not of grammar but of linguistics.  Thus, bull/cow, dog/bitch, cock/hen, boar/sow, ram/ewe, actor/actress -- man/woman -- all identify non-arbitrary heritable traits, independent and regardless of phonologic, syntactic and semantical abstractions.

Best practice moves from what is clear, direct and normal, to what is statistically and phenomenologically abnormal.  

J