# Glossary - X, Y, Z
### X
A fifth character appearing at the end of a security's ticker symbol that identifies the security as a mutual fund. For example, the symbol for the PRIMECAP Odyssey Stock Fund (POSKX) ends in an X to denote that the security is a mutual fund.
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### Yield Curve
A plot of treasury yields across the various maturities at a specific point in time. At the front (left) of the yield curve are [T-Bills](https://chartschool.stockcharts.com/table-of-contents/glossary-t#t-bill) with maturities of 12, 26, and 52 weeks. In the middle are Treasury Notes with maturities of 2, 5, and 10 years. At the end (right) of the yield curve are Treasury Bonds with maturities of 20 and 30 years. In a normal yield curve, yields rise as the maturities increase. If the yield on shorter maturities is higher than that of longer maturities, then an inverted yield curve exists. An inverted yield curve is a sign of tight money and is bearish for stocks. See our ChartSchool article on the [Yield Curve](https://chartschool.stockcharts.com/table-of-contents/chart-analysis/chart-types/yield-curve).
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### ZigZag
An overlay consisting of straight lines that connect significant tops and bottoms on a price graph. Its user-configurable parameter allows chartists to define “significant” as a certain percentage price change. The overlay will ignore all price changes below this percentage, highlighting important movements and ignoring noise on the chart. The ZigZag overlay does not predict trends and should not be used on its own. See our ChartSchool article on [ZigZag](https://chartschool.stockcharts.com/table-of-contents/technical-indicators-and-overlays/technical-overlays/zigzag).
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