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A capital H or theta of a variable, zero then one.
Also known as: Unit step function, Heaviside function, Step function
Sometimes confused with: Theta function
The Heaviside step is the switch: zero before the origin and one after it. Its value exactly at zero is a genuine convention rather than a fact — some texts say 0, some 1, some ½ — and the choice matters in Fourier work and nowhere else.
Denotes the unit step function: zero for negative argument and one for positive.
Contexts: Mathematics
Has no agreed value at the origin; 0, 1 and ½ are all in use, and the half-value is chosen where Fourier inversion is intended.
Contexts: Mathematics
Is the integral of the Dirac delta, which is the cleanest statement of how the two relate.
Contexts: Mathematics
A capital letter H or a Greek theta followed by a bracketed variable, drawn as a horizontal line stepping up to a higher horizontal line.