In financial economics, a liquidity crisis refers to an acute shortage (or "drying up") of liquidity. Liquidity is a catch-all term that may refer to several different yet closely related concepts. Among other things, it may refer by market liquidity (the ease with which an asset can be converted into a liquid medium e.g. cash), funding liquidity (the ease with which borrowers can obtain external funding), or accounting liquidity (the health of an institution’s balance sheet measured in terms of its cash-like assets). Additionally, some economists define a market to be liquid if it can absorb "liquidity trades" (sale of securities by investors to meet sudden needs for cash) without large changes in price. This shortage of liquidity could reflect a fall in asset prices below their long run fundamental price, deterioration in external financing conditions, reduction in the number of market participants, or simply difficulty in trading assets.