It is easier to categorize the following way:
1. There are four categories of people following the Buddha’s Path.
– Bhikkhu, Bhikkuni (female), and upāsaka, upāsikā (female). Of course, the former two are monks and the latter are laypeople.
– Then anyone from all the four categories who are at or above the Sotapanna Anugami stage (i.e., those of the Noble Lineage) belongs to the “Sangha” category.
2. These days, it has become common to categorize bhikkhus to be synonymous with “Sangha.” But that is not really correct.
– The “Triple Gems” should be Buddha, Dhamma (Buddha Dhamma), and Sangha (Noble Persons.)
– For example, Devadatta was a bhikkhu, but he never belonged to the “Sangha” category.