is a vector space and .
The set is linearly independent if no two distinct finite linear combinations of elements of can be equal vectors.
Other words: there is only one way to express a given vector using the linear combination of elements in .
A lemma
Statement: If is linearly independent and
Then
Proof
In case of a linearly independent set, having all the coefficients as zeroes is a trivial way to get the zero vector that always works. But due to the definition of linear independence, this is the only way to construct .
If is not linearly dependent, then it is said to be linearly dependent.
Properties
If , then is linearly dependent
Proof: in this case we have at least two ways to construct , so cannot be linearly independent anymore.
If is linearly dependent and , then is linearly dependent.
Proof: we have with and not all being zero the same is true for since it has the same elements still.
If is linearly independent and , then is linearly independent.
Proof: this is the contrapositive of the previous.