so·lum 
(sōləm)
(sōləm)n. pl. so·la (-lə) or so·lums
The upper layers of a soil profile in which topsoil formation occurs.
[Latin, base, ground.]
- limina
- liminal
- liminality
- liminally
- limit
- limitable
- limitary
- limitation
- limit-cycle
- limited
- limited access highway
- limited company
- limited edition
- limited liability company
- limited liability partnership
- limitedly
- limitedness
- limited partnership
- limited war
- limiter
- limites
- limiting
- limitless
- limitlessly
- limitlessness