diff --git a/fasta.cabal b/fasta.cabal
--- a/fasta.cabal
+++ b/fasta.cabal
@@ -10,7 +10,7 @@
 -- PVP summary:      +-+------- breaking API changes
 --                   | | +----- non-breaking API additions
 --                   | | | +--- code changes with no API change
-version:             0.10.0.0
+version:             0.10.1.0
 
 -- A short (one-line) description of the package.
 synopsis:            A simple, mindless parser for fasta files.
@@ -47,7 +47,8 @@
 
 library
   -- Modules exported by the library.
-  exposed-modules:    Data.Fasta.String,
+  exposed-modules:    Data.Fasta.Category,
+                      Data.Fasta.String,
                       Data.Fasta.String.Types,
                       Data.Fasta.String.Parse,
                       Data.Fasta.String.Translation,
diff --git a/src/Data/Fasta/Category.hs b/src/Data/Fasta/Category.hs
new file mode 100644
--- /dev/null
+++ b/src/Data/Fasta/Category.hs
@@ -0,0 +1,20 @@
+-- Category Module
+-- By Gregory W. Schwartz
+
+{- | Collects all functions pertaining to the categorization of nucleotides
+- or amino acids
+-}
+
+module Data.Fasta.Category where
+
+-- Algebraic
+data Hydrophobicity = Hydrophobic | Neutral | Hydrophilic
+                      deriving (Eq, Ord, Read, Show)
+
+-- | Returns the hydrophobicity of an amino acid
+aaToHydrophobicity :: Char -> Either String Hydrophobicity
+aaToHydrophobicity x
+    | x `elem` "IVLFCMW" = Right Hydrophobic
+    | x `elem` "AGTSYPH" = Right Neutral
+    | x `elem` "NDQEKR"  = Right Hydrophilic
+    | otherwise          = Left (x : " is not a valid amino acid")