slim
Stunning is a synonym for beautiful. It begins with S.
A synonym for "thinner" could be "slimmer" or "leaner."
sly
sympathy
sinceresternsolemnsevere
The synonym of "cosy" that begins with an "s" is "snug." Both words convey a sense of warmth, comfort, and being tucked in.
Spear is a synonym for lance. It begins with the letter S.
Surface is a synonym for to appear. It begins with the letter S.
"actual" begins with "a" and is a synonym for "real".
Stock is a synonym of product. It begins with the letter s.
Snow job is a synonym for deception. It begins with the letter S.
Substantial is a synonym for large amount. It begins with S.