From earlier posts you may have noticed my inability to distinguish between chromasomes and chromatids...unfortunately I am still unable to do this.

So at the moment I think this to be true:
My cell normally has 46 chromosomes.
During the S phase of interphase, my DNA duplicates via semi-conservative replication. Do I now have 92 chromsomes (I'm kinda sure this is wrong) or do I have 92 chromatids and 46 chromosomes? Is it called a chromosome before replication when it is linear and wrapped around histone proteins . And is it also called a chromosome when it is X shaped and the X shaped chromosome is made of sister chromosomes which are a copy of the linear looking chromosome.

At anaphase the 42 "chromosomes" are split at the centromere and when they seperate the seperate parts are called chromatids. When do they go back to being chromsomes?

I really enjoy genetics but I can't seem to grasp these simple definitions! It seems like the word chromosme is used to describe many differnt structure of the DNA.

Essentially want to know how many chromsomes are in each phase of mitosis in addition to what exactly a chromosome is?

Here is the way I think about it: before S phase, a typical human cell contains 46 chromosomes. During S phase, all 46 chromosomes are replicated. Because they are identical copies, it is perfectly fine to say that there are now 92 (46 + 46) chromosomes in the cell. However, the term 'chromatid' is used to describe them until cell division is complete. In other words: a chromatid is just what we a call a chromosome during cell division. Also, because the chromatids are stuck together after replicating, it is also reasonable to say that there are 46 pairs of chromatids (or chromosomes) at the end of S phase.

If the cell goes through mitosis (normal cell division) those 46 pairs will separate and the two daughter cells will have 46 chromosomes.

If the cell goes through meiosis (gamete formation) each chromatid pair will pair up with another (homologous) chromatid pair to form a group of four chromatids called a tetrad (my textbook also calls this a bivalent). There should be 23 tetrads in a human cell at the beginning of meiosis. The cell then divides twice with the chromatids separating each time. This results in four cells each of which contains 23 chromosomes (46/2). These cells are called gametes. When one gamete combines with another gamete, a zygote is formed which has 46 chromosomes. The zygote then goes through mitosis to form more cells with 46 chromosomes and those cells make up the embryo.

I have been teaching genetics for four years now and I find that this concept is one of the biggest stumbling blocks for students (for obvious reasons). If it helps, whenever you see the word 'chromatid' just replace it with 'chromosome' since, for most purposes, they mean the same thing.