Features can only be declared for one type. If two types need the same feature, they need to have a common supertype from which to inherit it. You might hit this error if you happen to try to reuse a feature name already in use in the matrix, or if you try to declare a feature for two types at the same time (e.g., FORM on verb and prep) instead of putting it on a supertype.

NB: You can of course mention features on multiple types, and often need to in order to constrain their values appropriately. They just need to be introduced on a supertype to all types that they are appropriate for. This doesn't mean that e.g., trans-verb-lex needs to inherit from noun in order to constrain a value of CASE on one of its arguments. In the example below, CASE remains a feature of noun, which happens to be the value at the end of a path inside verb-lex.

trans-verb-lex := verb-lex & transitive-lex-item &
   [ SYNSEM.LOCAL.CAT.VAL.COMPS < [ LOCAL.CAT.HEAD noun &
                                            [ CASE acc ] ] > ].

• I'm trying to add a new feature, and the LKB doesn't like it. What should I do?

• When I load my grammar, I get "no possible type for features (...) at path (...)". What is causing this?

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