Important airspeed definitions:
\[
\boxed{
\begin{aligned}
\text{IAS} &\rightarrow \text{Indicated Air Speed}
\text{CAS} &\rightarrow \text{IAS corrected for instrument and position errors}
\text{EAS} &\rightarrow \text{CAS corrected for compressibility}
\text{TAS} &\rightarrow \text{EAS corrected for air density}
\end{aligned}
}
\]