DEFINITION of 'Time Series'
A sequence of numerical data points in successive order, usually occurring in uniform intervals. In plain English, a time series is simply a sequence of numbers collected at regular intervals over a period of time.
INVESTOPEDIA EXPLAINS 'Time Series'
Time series analysis can be useful to see how a given asset, security or economic variable changes over time or how it changes compared to other variables over the same time period. For example, suppose you wanted to analyze a time series of daily closing stock prices for a given stock over a period of one year. You would obtain a list of all the closing prices for the stock over each day for the past year and list them in chronological order. This would be a oneyear, daily closing price time series for the stock.
Delving a bit deeper, you might be interested to know if a given stock's time series shows any seasonality, meaning it goes through peaks and valleys at regular times each year. Or you might want to know how a stock's share price changes as an economic variable, such as the unemployment rate, changes.

Correlation
In the world of finance, a statistical measure of how two securities ... 
Covariance
A measure of the degree to which returns on two risky assets ... 
Indicator
Statistics used to measure current conditions as well as to forecast ... 
Trend
The general direction of a market or of the price of an asset. ... 
Heteroskedastic
A measure in statistics that refers to the variance of errors ... 
Homoskedastic
A statistics term indicating that the variance of the errors ...

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