invisible, indivisible

Invisible or invisible describes something that can't be seen--
Many people believe that the economy is guided by an "invisible hand".
People keep bumping into him, as if he's invisible.
Germs are invisible to the naked eye; they can only be seen with a microscope.

Indivisible or indivisible describes something that can't be divided--
"One nation, under God, indivisible..."
Many people consider marriage an indivisible union.

Now that you know that, you can say--
"An invisible bond of loyalty renders them an indivisible unit."

Note--"visible" describes something that can be seen--
The sign is visible from the highway.
A look of disbelief was visible on his face.
Note # 2 --"Divisible" describes something that can be divided, meaning cut or separated into pieces--
This land is divisible into one-acre lots.
Divisible is more commonly used as a math term--
Is 24 divisible by 4? ( yes )
17 is not divisible by 4.
Note # 3-- not to be confused with "invincible", meaning impossible to defeat or conquer--
Superman is the man of steel; he is invincible.