A perennial stream or perennial river is a stream or river (channel) that has continuous flow in parts of its stream bed all year round during years of normal rainfall. "Perennial" streams are contrasted with "intermittent" streams which normally cease flowing for weeks or months each year, and with "ephemeral" channels that flow only for hours or days following rainfall.

The Scientific Services Bureau operates one of the largest full-service crime laboratories in the United States. A staff of 198 members provides forensic science support to all Los Angeles County law enforcement agencies, except the Los Angeles Police Department. Approximately one half of the nearly 70,000 cases submitted annually to the Crime Lab is from Sheriff's Department investigators , while the remainder is from local, state, and federal agencies. Since 1989 the Scientific Services Bureau has been an accredited laboratory through the American Society of Crime Laboratory Directors/Laboratory Accreditation Board (ASCLD/LAB).

In 2011, the Ohio Turnpike raised its limit to 70 and recorded its lowest traffic fatality rate ever that year. The higher speed limit attracts travelers to use the safer, limited-access, divided highways of the interstates from more traditional roads. That makes both types of roads safer.

The Doppler effect (or Doppler shift), named after the Austrian physicist Christian Doppler, who proposed it in 1842 in Prague, is the change in frequency of a wave (or other periodic event) for an observer moving relative to its source. It is commonly heard when a vehicle sounding a siren or horn approaches, passes, and recedes from an observer. The received frequency is higher (compared to the emitted frequency) during the approach, it is identical at the instant of passing by, and it is lower during the recession.

Water polo, or water ball, is a team water sport. The playing team consists of six field players and one goalkeeper. The winner of the game is the team that scores the most goals. Game play involves swimming, treading water (using a sort of kicking motion known as "eggbeater kick"), players passing the ball while being defended by opponents, and scoring by throwing the ball into a net defended by a goalie. "Man-up" (or "power play") situations occur frequently. Water polo, therefore, has strong similarities to the land-based game of team handball.