What exactly, then, is an urban slum? Earlier research has put forward a variety of interpretations, but as yet no broad consensus on the precise meaning of this term has been reached. However, concentrating on its most visible characteristics, a slum may be tentatively described as a densely populated area inhabited by low-income people, particularly the unemployed. Here, single tenants and nuclear families were packed into rows of narrow, decrepit, one-story wooden tenements (back-street nagaya) where poor housing conditions facilitated the spread of epidemics and where the danger of fires becoming general conflagrations was particularly great. Slum inhabitants used a special argot among themselves and in some instances regarded non-slum dwellers with suspicion and dislike. However, even where all of these conditions were not met, one could still speak of any over-populated area characterized by poorly constructed wood dwellings as a sulm.