Clarify shape requirements for 𝕨 in •rand.Range

1 files changed, 1 insertions, 1 deletions

diff --git a/spec/system.md b/spec/system.md
index 15ada7b4..71d4fb9d 100644
--- a/spec/system.md
+++ b/spec/system.md
@@ -218,7 +218,7 @@ More accurately the modifier `•_maxTime_` *may* fail if execution of `𝔽` ta
 | `Deal`    | A simple random sample of `𝕨⊣𝕩` elements of `↕𝕩`
 | `Subset`  | A sorted SRS of `↕𝕩`, with `𝕨` elements if given
 
-For each of these functions, `𝕩` is a natural number. For `Range`, `𝕨` must be a valid shape if given, and for `Deal` and `Subset` it's a natural number less than or equal to `𝕩`. All selections are made uniformly at random, that is, each possible result is equally likely. A simple random sample (SRS) of `k` elements from list `s` is a list of `k` distinct elements of `s` in any order. Both the choice of elements and their ordering must be uniformly random. [Recommended algorithms](../implementation/primitive/random.md#simple-random-sample) for SRS selection are variants of a partial Knuth shuffle.
+For each of these functions, `𝕩` is a natural number. For `Range`, `𝕨` must be a valid shape (natural number, or list or unit array of natural numbers) if given, and for `Deal` and `Subset` it's a natural number less than or equal to `𝕩`. All selections are made uniformly at random, that is, each possible result is equally likely. A simple random sample (SRS) of `k` elements from list `s` is a list of `k` distinct elements of `s` in any order. Both the choice of elements and their ordering must be uniformly random. [Recommended algorithms](../implementation/primitive/random.md#simple-random-sample) for SRS selection are variants of a partial Knuth shuffle.
 
 When `𝕨` isn't given, `Deal`'s result contains all elements of `↕𝕩`, making it a random shuffle of those values, or random permutation. In `Subset`, a random choice is made uniformly from the `2⋆𝕩` subsets of `↕𝕩`, so that a subset of any length may be returned.