Rearrangement-invariance in function spaces can be viewed as a kind of generalization of 1-symmetry for Schauder bases. We define subrearrangement-invariance in function spaces as an analogous generalization of 1-subsymmetry. It is then shown that every rearrangement-invariant function space is also subrearrangement-invariant. Examples are given to demonstrate that not every function space on (0, ∞) admits an equivalent subrearrangement-invariant norm, and that not every subrearrangementinvariant function space on (0, ∞) admits an equivalent rearrangementinvariant norm. The latter involves constructing a family of function spaces inspired by D.J.H. Garling, and we further study them by showing that they contain copies of ℓ p .