can you just concentrate on this?!

Concentration is defined as the abundance of a constituent divided by the total volume of a mixture. In chemistry there are four different types of concentration: mass concentration, molar concentration, number concentration, and volume concentration.

here are examples of the four types:

mass concentration:

The mass concentration ρ_i is defined as the mass of a constituent m_i divided by the volume of the mixture V:

The SI-unit is kg/m³.

molar concentration:

The molar concentration c_i is defined as the amount of a constituent n_i divided by the volume of the mixture V:

The SI-unit is mol/m³. However, more commonly the unit mol/L is used.

number concentration:

The number concentration C_i is defined as the number of entities of a constituent N_i in a mixture divided by the volume of the mixture V:

The SI-unit is 1/m³.

volume concentration:

The volume concentration ϕ_i (also called volume fraction) is defined as the volume of a constituent V_i divided by the volume of all consituents of the mixture V prior to mixing:

The SI-unit is m³/m³.

These are all related to chemistry.