Hello Irealltdonocare: Hm-m-m-m... well... the Skeezyks is no expert in these matters... unless one equates a lifetime of being transgender with having developed some small amount of expertise on the subject. Different people use the terms "transgender" & "transsexual" differently. To my knowledge, there are no firm definitions. Here is a definition of the term "transgender" from Wikipedia:
"Transgender people are people who have a gender identity, or gender expression, that differs from their assigned sex. Transgender people are sometimes called transsexual if they desire medical assistance to transition from one sex to another. Transgender is also an umbrella term: in addition to including people whose gender identity is the opposite of their assigned sex (trans men and trans women), it may include people who are not exclusively masculine or feminine (people who are genderqueer, e.g. bigender, pangender, genderfluid, or agender). Other definitions of transgender also include people who belong to a third gender, or conceptualize transgender people as a third gender. Infrequently, the term transgender is defined very broadly to include cross-dressers, regardless of their gender identity."
I would have to admit that, for me, a lot of this is beyond my understanding. Back when I was young, there were boys & there were girls. And if you didn't happen to fit neatly into one of those categories, you darn well kept it to yourself if you knew what was good for you.

But, I think the point is "transgender" includes individuals who "want to be the opposite gender". But it can also denote individuals with other gender identity perspectives as well.
The thing is... there are no tests with which one can be "diagnosed" as being transgender.

Each of us has to decide in our own minds if we are, or are not, transgender... assuming that we feel the need to do that. The reality is it really isn't even necessary. Each of us simply is who s/he is. And there are many resting places along the gender identity continuum. Wherever one comes to rest... it's all good.
I personally find the terminology "wanting to be the opposite gender" to be curious.

I know the term "wanting" gets used a lot. I've even used it myself!

But, really, in my case I never "wanted" to be the opposite gender.

But all of my life I have struggled with a compulsion, if you will, to be the opposite gender (in my case... female.) I would have much preferred to just be what I was born... male.

But as far back as I can remember, I have been driven to be female.
One writer I have read referred to this as "the transsexual imperative". I never did anything to resolve this compulsion. And, either because of it or in addition to it, I've also struggled with depression, anxiety, & other mental health problems.

As a result, I have great compassion for those who struggle with these issues. It is getting easier nowadays to be trans. But it can still be a challenge. So if this is something you struggle with, or if you are asking this question because you care for someone who is, my heart goes out to you... or them.
P.S. Thanks for posting this. I enjoyed replying to it. I hope something I wrote is of some value.