Terminology for 'prevalence' when it's number of people and not a proportion? 'Prevalence' is usually used to describe a proportion or rate, e.g. '5% $\pm$ 2% of the population are Blue'. What do you call this when you estimate the actual number of people in a population with a trait, for example, with survey data and a Horvitz-Thompson estimator, e.g., '500 $\pm$ 100 people are Blue'. Best to just write it out? As in, 'The estimated prevalence of Blueness implied that approximately 500 $\pm$ 100 were Blue'.
 A: Incidence and prevalence are two terms which are often used in relation to some disease. Incident cases refers to new cases while prevalence refers to old+new cases. You have terms like incidence number and incidence rate. Similarly, you have prevalent number of cases and prevalence rate. Let us say that in a certain community of 1000 there are 40 person with blue eyes. Now, this can be referred simply as number of people with blue eyes are 40 in the population of 1000. Once you express this as proportion of population i.e., 40/1000 = 0.04 or 4%,  you can say that there is 4% population with blue eyes. So, a careful researcher will use prevalence and prevalence rate in different contexts as mentioned above. 
What is asked by you is estimated number with trait blue is 500±100. Here, your estimate of people with trait blue is based on a sample drawn by you. With another sample, this number may change. So, you want to give a confidence limit of number of people with trait blue which is 500±100. 
A: "Estimated prevalence of Blueness implied that approximately 500 ± 100 individuals in our sample of $n$ individuals would be Blue.  This equates to a prevalence rate of $x\% \pm y\%$"
