imperial ancestor worship
禘 centers on a formal ritual of worship directed toward imperial ancestors, a specific ceremonial practice rather than a general concept of worship.
禘 combines 示 (altar, ritual) with 帝 (emperor, sovereign), suggesting a ritual specifically connected to the imperial line or ancestors. The exact historical development is uncertain, but the component relationship is consistent with its meaning.
The left side 示 represents an altar or ritual, and the right side 帝 is the emperor. Picture a solemn ceremony at the imperial altar honoring past emperors.
For テイ, imagine a tea ceremony at the imperial altar: tea -> テイ, and the ritual honors the ancestors.