diff --git a/Paper/Open-Vocabulary Semantic Segmentation.md b/Paper/Open-Vocabulary Semantic Segmentation.md
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@@ -1,4 +1,4 @@
 
 
 ### Vocabularies
-1. ground-truth masks: 
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+1. ground-truth masks: refer to the manually annotated masks or pixel-level labels that are used to define the correct segmentation of objects in an image. Each pixel in the ground-truth mask is assigned a specific class label corresponding to the object or region it belongs to.
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