Gum and Red gum

Gum noun - Any of various substances (soluble in water) that exude from certain plants; they are gelatinous when moist but harden on drying.

Red gum and gum are semantically related. In some cases you can replace phrase "Red gum" with "Gum", this terms are similar.

Red gum noun - Reddish-brown wood and lumber from heartwood of the sweet gum tree used to make furniture.

Gum and red gum are semantically related. Sometimes you can use "Gum" instead a noun phrase "Red gum".