In the American educational system 101 indicates an introductory course, often with no prerequisites. The meaning has been extended to include any introduction to the basics of anything.
a number cruncher
Meaning:
a number cruncher refers to someone whose job is to work with numbers and mathematics. It may also refer to a computer that is able to solve complicated problems of mathematics.
at sixes and sevens
Meaning:
Someone is in a state of confusion or not very well organized.
be on cloud nine
Meaning:
feel extreme happiness or elation
by the numbers
Meaning:
If you do something by the numbers, you are doing it in a strict, mechanical way, without using your imagination or creativity.
count to ten
Meaning:
If someone asks you to count to ten, they are advising you to take a moment to calm down. The phrase is often used when someone is angry.
do a number on
Meaning:
The phrase to do a number on is an idiomatic expression that means to treat harshly, to hurt or to damage
dressed up to the nines
Meaning:
when someone is dressed up to the nines, they are wearing fashionable or formal clothes for a special occasion.
feel like a million
Meaning:
To feel like a million means to feel well and healthy, both physically and mentally.
fifth column
Meaning:
refers to a group within a country at war who are sympathetic to or collaborate with its enemies.
give me five
Meaning:
If you say give me five, you want someone to slap your open hand as a greeting or to show joy.
keep count of something
Meaning:
If you keep count of something, you remember or record a number as it changes over a period of time.