| Labeorphily |
Collection and study of beer bottle labels |
| Larithmics |
Study of population statistics |
| Laryngology |
Study of larynx |
| Lepidopterology |
Study of butterflies and moths |
| Leprology |
Study of leprosy |
| Lexicology |
Study of words and their meanings |
| Lexigraphy |
Art of definition of words |
| Lichenology |
Study of lichens |
| Limacology |
Study of slugs |
| Limnobiology |
Study of freshwater ecosystems |
| Limnology |
Study of bodies of fresh water |
| Linguistics |
Study of language |
| Lithology |
Study of rocks |
| Liturgiology |
Study of liturgical forms and church rituals |
| Loimology |
Study of plagues and epidemics |
| Loxodromy |
Study of sailing along rhumb-lines |