| Language | Reflex(es) | Gloss | Grammar | Sources |
|---|
| English |
| Old English | underneoþan | underneath | adv | W7 ASD LRC |
| Old English | under | under, among, before, during | prep | W7 ASD LRC |
| Middle English | undernethe | underneath | prep | W7 LRC |
| Middle English | inferior | inferior | adj | W7 LRC |
| Middle English | infernal | infernal | adj | W7 LRC |
| Middle English | under | under | prep | W7 LRC |
| English | underneath | directly below, close beneath | prep | AHD W7 LRC |
| English | Underharrow | Rohan village in Tolkien: The Lord of the Rings | prop.n | LRC |
| English | Underhill | Hobbiton family in Tolkien: The Lord of the Rings | prop.n | LRC |
| English | inferior | lower, situated below | adj | AHD W7 LRC |
| English | infernal | re: nether world of dead | adj | AHD W7 LRC |
| English | inferno | place/state resembling/suggesting hell | n | AHD W7 LRC |
| English | infra- | below | pfx | AHD W7 LRC |
| English | U-boat | Austro-Hungarian/German submarine | prop.n | LRC |
| English | under | in(to) position below/beneath something | adv | AHD W7 LRC |
| English | Undertowers | Shire town in Tolkien: The Lord of the Rings | prop.n | LRC |
| West Germanic |
| Old Frisian | under | under | prep | ASD LRC |
| Dutch | onder | under | prep | TLL LRC |
| Old Saxon | undar | under | prep | ASD LRC |
| Old High German | untar | under | prep | W7 LRC |
| German | U-boot | U-boat | n.neut | W7 LRC |
| German | unter | under | prep | LRC |
| German | Unterseeboot | submarine, lit. undersea boat | n.neut | W7 LRC |
| North Germanic |
| Icelandic | undir | under | prep | ASD LRC |
| Danish | under | in, during, under | prep | TLL LRC |
| Swedish | under | in, during, under | prep | TLL LRC |
| East Germanic |
| Gothic | undar | under | prep | ASD LRC |
| Italic |
| Latin | inferior | inferior, less good | adj.comp | W7 LRC |
| Latin | inferus, inferi | low, nether; lower part | adj | LRC |
| Latin | infrā | below, under | adv | W7 LRC |
| Late Latin | infernalis | infernal | adj | W7 LRC |
| Late Latin | infernus | infernal, of hell, under the earth | adj | W7 LRC |
| Old French | infernal | infernal, of hell | adj | W7 LRC |
| Italian | fra | in | prep | TLL LRC |
| Italian | infèrno | hell, horror, inferno | n.masc | W7 LRC |
| Indo-Iranian |
| Sanskrit | adha | under, below | prep | W7 LRC |