| 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 |