Fix typo in IDL specs
This closes #1880.
diff --git a/doc/specs/idl.md b/doc/specs/idl.md
index ac35368..9439bee 100644
--- a/doc/specs/idl.md
+++ b/doc/specs/idl.md
@@ -126,7 +126,7 @@
- Read: Optional fields may, or may not be part of the input stream.
- Default values: are written when the isset flag is set
-Most language implementations use the recommended pratice of so-called "isset" flags to indicate whether a particular optional field is set or not. Only fields with this flag set are written, and conversely the flag is only set when a field value has been read from the input stream.
+Most language implementations use the recommended practice of so-called "isset" flags to indicate whether a particular optional field is set or not. Only fields with this flag set are written, and conversely the flag is only set when a field value has been read from the input stream.
#### default requiredness (implicit)