Saskatoon is divided into east and west sides by the South Saskatchewan River. It is then divided into Suburban Development Areas (SDA) which are composed of neighbourhoods. Street addresses are demarcated into north and south (for avenues aligned in those directions) and similar east and west (for streets aligned in those directions). West of the river the demarcation line for north and south addresses is 22nd Street, while east and west are divided by Idylwyld Drive (north of 20th Street) and Avenue A (south of 20th). On the east side, Lorne Avenue demarcates east and west while Aird Street marks the north/south boundary, except in the Sutherland community where a separate east/west demarcation takes place with Central Avenue as the boundary (there is, however, no separate north/south divide). As a result of the unusual demarcation on the east side, few streets actually carry a "North" or "West" designation.