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paper.md

@@ -34,7 +34,7 @@ River networks are crucial in hydrologic and Earth system models. Accurately rep
 For hydrologic modelers, river networks are a key input for hydrologic models. 
 While some hydrologic models accept vector-based river networks [@Schwenk:2021], others only accept mesh cell-based, which requires a generation method from the vector-based river network. 
 Currently, generating a mesh cell-based river network from a given vector-based river network and arbitrary computational mesh is a major challenge.
-Existing methods are typically limited to structured rectangular meshes, such as 30m x 30m cartesian grids for high-resolution watershed-scale modeling or 0.5 degree x 0.5 degree geographic grids for global climate modeling. 
+Existing methods are typically limited to structured rectangular meshes, such as 30m x 30m cartesian grids for high-resolution watershed-scale modeling or 0.5 degree x 0.5 degree geographic grids for global climate modeling. In PyFlowline, we define structured meshes (e.g., lat-lon, raster files with projections, and hexagon) as those with fixed cell sizes and shapes and unstructured meshes as those with variable cell sizes and shapes.
 
 Structured mesh-based methods use fixed cartesian or geographic cell sizes, which have several limitations: (1) they perform poorly at coarse resolution (>1km), and (2) they cannot be seamlessly coupled with other unstructured mesh-based hydrologic models such as oceanic models [@Engwirda:2021]. In contrast, unstructured meshes offer a flexible structure with variable grid-cell sizes and shapes. This flexibility makes them ideal for adapting to complex geometry such as river channels and coastlines. Besides, unstructured meshes provide the flexibility to couple different hydrologic models under a unified framework.
 Thus, unstructured meshes are increasingly being adopted in hydrologic modeling.