While I was writing a man page, an issue arising, the code is like:

Something is
.B bold
.

.B is a font setting macro of groff_man(7). The period won’t be in final output because it’s ignored according to groff(7):

. Empty line, ignored. Useful for structuring documents.

And \. doesn’t work either, it’s not the escape I’d hope is:

\. The same as a dot (.). Necessary in nested macro definitions so that \\.. expands to ...

A quick search returned an answer of how to escape period, which is at the beginning of a line:

Something is
.B bold
\[char46]

It works, but later I found another way to achieve something even better with escape sequence:

Something is \fBbold\fP.

It’s better because, in my case, the “bold” can get broken into two lines with a hyphen, and spacing between words looks nicer.

I am no expert of writing man pages, the pages I have written could be counted with just my ten fingers, there probably is a better way than these two above. For now, I will settle down with them.