Real Dictionary

strength
uncountable noun: If you refer to the strength of a currency, economy, or industry, you mean that its value or success is steady or increasing.
uncountable noun: If you refer to the strength of a feeling, opinion, or belief, you are talking about how deeply it is felt or believed by people, or how much they are influenced by it.
uncountable noun: Someone's strength in a difficult situation is their confidence or courage.
uncountable noun: The strength of a person, organization, or country is the power or influence that they have.
uncountable noun: The strength of an object or material is its ability to be treated roughly, or to carry heavy weights, without being damaged or destroyed.
uncountable noun: Your strength is the physical energy that you have, which gives you the ability to perform various actions, such as lifting or moving things.
variable noun: Someone's strengths are the qualities and abilities that they have which are an advantage to them, or which make them successful.

strength in American English
the state or quality of being strong; force; power; vigor
noun: the quality or state of being strong; bodily or muscular power; vigor

strength in British English
noun: the state or quality of being physically or mentally strong

strength in the Pharmaceutical Industry
noun: The strength of a chemical or drug is the concentration of the active ingredient in it.