l (length)
A lowercase l is the abbreviation for length in formulas, such as A = l × w.
L (liter)
A capital L is the symbol for liter, a metric unit of capacity.
Lateral area
The total area of the side faces of a prism or pyramid, or the curved surface of a cylinder or cone, not counting the bases.
Lateral face
A face of a prism or pyramid that is not a base.
Law of cosines
A formula relating the sides and one angle of any triangle: c² = a² + b² − 2ab cos C.
Law of sines
In any triangle, each side divided by the sine of its opposite angle gives the same ratio: a/sin A = b/sin B = c/sin C.
LCD
Short for least common denominator.
LCM
Short for least common multiple.
Leading coefficient
The coefficient of the term with the highest power in a polynomial written in standard form.
Leap year
A year with 366 days instead of 365. February gets a 29th day, usually every 4 years.
Least common denominator
The least common multiple of the denominators of two or more fractions, used to add or compare them.
Least common multiple
The smallest positive number that is a multiple of two or more numbers.
Leg (of a right triangle)
Either of the two sides that form the right angle in a right triangle.
Length
The distance from one end of something to the other, usually its longest dimension.
Less than
Smaller in value than, written with the symbol <. For example, 3 < 8.
Less than or equal to
At most as large as, written with the symbol ≤. x ≤ 3 includes 3 and every number below it.
Like denominators
Fractions with the same denominator, also called like fractions. To add them, add the numerators and keep the denominator.
Like terms
Terms with the same variables raised to the same powers, such as 3x and 5x. They can be combined.
Limit
The value a function approaches as the input gets closer and closer to a certain number.
Line
A straight path of points that goes on forever in both directions. It has no thickness.
Line graph
A graph that uses points joined by line segments to show how data change, often over time.
Line of best fit
A straight line drawn through a scatter plot that best shows the trend of the data; also called a trend line.
Line of symmetry
A line that divides a figure into two halves that are mirror images.
Line plot
A graph that shows data by placing an X or dot above each value on a number line.
Line segment
Part of a line with two endpoints. It has a definite length.
Linear equation
An equation whose graph is a straight line, such as y = 2x + 1.
Linear function
A function that changes at a constant rate, so its graph is a straight line: f(x) = mx + b.
Linear inequality
An inequality whose boundary is a straight line, such as y < x + 1. Its solutions are a shaded half-plane.
Linear measurement
Measuring distance or length along a line, in units such as centimeters, meters, inches or feet.
Linear pair
Two adjacent angles whose outer sides form a straight line. They add up to 180°.
List price
The regular price of an item before any discount; also called the marked price.
Liter
A metric unit of capacity equal to 1000 milliliters, a little more than a quart or about ¼ of a US gallon.
Literal equation
An equation with two or more variables, such as a formula, that can be solved for one of them.
Logarithm
The exponent a base must be raised to in order to get a given number. log₂ 8 = 3 because 2³ = 8.
Long division
A step-by-step method for dividing large numbers by hand: divide, multiply, subtract, bring down.
Lower quartile
Another name for the first quartile (Q1), the median of the lower half of the data.
Lowest terms
A fraction is in lowest terms when its numerator and denominator have no common factor except 1, such as 3/4.