Cryptic crosswords often use abbreviations to clue individual letters or short fragments of the overall solution. These include: * Any conventional abbreviations found in a standard dictionary, such as: * "current": AC (for "alternating current"); less commonly, DC (for "direct current"); or even I (the symbol used in physics and electronics) * Roman numerals: for example the word "six" in the clue might be used to indicate the letters VI * The name of a chemical element may be used to signify its symbol; e.g., W for tungsten * The days of the week; e.g., TH for Thursday * Country codes: "Switzerland" can indicate the letters CH * ICAO spelling alphabet: where Mike signifies M and Romeo R * Conventional abbreviations for US cities and states: for example, "New York" can indicate NY