as follows
"The competition will feature three athletes, namely John, Sarah, and Mike."
Specifically; that is to say.
"The package contained three items, namely a notebook, a pen, and an eraser."
In plain English: Namely is used to specify exactly what you are talking about right after mentioning it generally.
"The invitation was sent to our guests, namely John and Sarah."
From Middle English namely, nameliche, namelike, equivalent to name + -ly. Cognate with Saterland Frisian nämmelk, West Frisian nammentlik, Dutch namelijk, German Low German nämlich, German nämlich, Danish nemlig, Swedish nämligen, Icelandic nefnilega.