1. Ahead of means closer to a destination than or in front of.
My friend arrived first, and was ahead of me in line.
2. Ahead of means before.
You are in a hurry; please go ahead of me.
3. Ahead of can mean more advanced than.
Because he was absent for two weeks, the other students in his class are ahead of him.
4. Phrasal verbs
get ahead (intransitive)—succeed
She has struggled all her life to get ahead.
get ahead of (nonseparable)—advance faster or further than someone else
They are rivals, always competing to get ahead of each other.
go ahead (intransitive)—Do it; begin now
I asked for permission, and they told me to go ahead.
Precautions while using Laboratory Thermometers
Liquid in glassthermometers
Liquidinglassthermometers are made of sealed glass and contain a fluid, usuallymercuryorred alcohol, whose volume changes relative to its temperature. The liquid expands as the temperature rises, rising in the tube and indicating the temperature.