论坛
lùn tán · HSK 7
forum (for discussion)
💬 论 (discuss) + 坛 (platform/arena) = a platform for discussion = forum
论 means to discuss or debate; 坛 is a raised platform or arena (same 坛 as in 讲坛 lecture platform). Put them together and you get a place built for debate — an online or public forum.
坛 — earth radical 土 + 云 (cloud/yun phonetic)
坛 is the simplified form of 壇, originally a phono-semantic compound with 土 (earth) giving the meaning of a raised earthen platform or altar, and 亶 supplying the sound. The simplified version swaps in 云 as a simpler phonetic. It later extended to mean a sealed jar or a community circle, as in 文坛 (literary world).