A bear market is when the price of an investment falls over time. It begins after prices have fallen 20 percent or more from their 52-week high.
https://www.thebalance.com/what-is-a-bear-market-difference-from-a-bull-3305814
Bear market versus market correction
A market correction is a period in which stock prices drop following a period of higher prices. The idea behind a correction is that because prices rose higher than they should've, falling prices serve the purpose of "correcting" the situation. One major difference between a bear market and a market correction is the extent to which prices fall. Bear markets occur when stock prices drop 20% or more, whereas corrections typically involve price drops around 10%. Furthermore, market corrections tend to last less than two months, whereas bear markets last two months or longer.
https://www.fool.com/knowledge-center/bear-market.aspx
bear mar·ket
/ˈˌbe(ə)r ˈmärkət/Submit
nounSTOCK MARKET
noun: bear market; plural noun: bear markets
a market in which prices are falling, encouraging selling.
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Bear market
A bear market is a general decline in the stock market over a period of time.[9] It is a transition from high investor optimism to widespread investor fear and pessimism. According to The Vanguard Group, "While there's no agreed-upon definition of a bear market, one generally accepted measure is a price decline of 20% or more over at least a two-month period."[10]
A smaller decline of 10 to 20% is considered a correction. Once a market enters correction or bear market territory, it isn't considered to have exited that territory until a new high is reached
https://en.wikipedia.org/wiki/Market_trend
https://www.thebalance.com/what-is-a-bear-market-difference-from-a-bull-3305814
Bear market versus market correction
A market correction is a period in which stock prices drop following a period of higher prices. The idea behind a correction is that because prices rose higher than they should've, falling prices serve the purpose of "correcting" the situation. One major difference between a bear market and a market correction is the extent to which prices fall. Bear markets occur when stock prices drop 20% or more, whereas corrections typically involve price drops around 10%. Furthermore, market corrections tend to last less than two months, whereas bear markets last two months or longer.
https://www.fool.com/knowledge-center/bear-market.aspx
bear mar·ket
/ˈˌbe(ə)r ˈmärkət/Submit
nounSTOCK MARKET
noun: bear market; plural noun: bear markets
a market in which prices are falling, encouraging selling.
Google.com search
Bear market
A bear market is a general decline in the stock market over a period of time.[9] It is a transition from high investor optimism to widespread investor fear and pessimism. According to The Vanguard Group, "While there's no agreed-upon definition of a bear market, one generally accepted measure is a price decline of 20% or more over at least a two-month period."[10]
A smaller decline of 10 to 20% is considered a correction. Once a market enters correction or bear market territory, it isn't considered to have exited that territory until a new high is reached
https://en.wikipedia.org/wiki/Market_trend
You can use technical definitions all that you like, but such technical definitions are not going to give you a very accurate place regarding the starting point, if the price went up 78x in 2 years (starting from about $250 in about October 2015 to December 2017) and even nearly 8x from about $2,500 to $19,666 in the most recent exorbitant rise of the last 4 months (from August to December) of that bull run.
Part of my reason for not conceding bear market until after breaking support below $6k, but in any case, calling the market is certainly a lagging indicator, because we are likely to also not know when we are in a bull market either, until we are in it for 6 months or more.