diff --git a/MANIFEST.in b/MANIFEST.in
index 1111bcd..6c2d974 100644
--- a/MANIFEST.in
+++ b/MANIFEST.in
@@ -1,3 +1,4 @@
 include archive/*
 include LICENSE
+include joy/defs.txt
 recursive-include joy *.py
diff --git a/joy/__main__.py b/joy/__main__.py
index e1f7b80..f6f2909 100644
--- a/joy/__main__.py
+++ b/joy/__main__.py
@@ -17,7 +17,7 @@
 #    You should have received a copy of the GNU General Public License
 #    along with Thun.  If not see <http://www.gnu.org/licenses/>.
 #
-import sys
+import argparse, io, pkg_resources
 from .library import initialize, inscribe
 from .joy import repl, interp
 from .utils.pretty_print import trace
@@ -25,7 +25,38 @@ from .utils.pretty_print import trace
 
 inscribe(trace)
 
-if '-q' in sys.argv:
+
+argparser = argparse.ArgumentParser(
+    prog='thun',
+    description='Joy Interpreter',
+    )
+argparser.add_argument(
+    '-d', '--defs',
+    action='append',
+    default=[
+        io.TextIOWrapper(
+            pkg_resources.resource_stream(__name__, 'defs.txt'),
+            encoding='UTF_8',
+            )
+        ],
+    type=argparse.FileType('r', encoding='UTF_8'),
+    help=(
+        'Add additional definition files.'
+        ' Can be used more than once.'
+        ),
+    )
+argparser.add_argument(
+    '-q', '--quiet',
+    help='Don\'t show the prompt.',
+    default=False,
+    action='store_true',
+    )
+
+
+args = argparser.parse_args()
+
+
+if args.quiet:
     j = interp
 else:
     j = repl
diff --git a/joy/defs.txt b/joy/defs.txt
new file mode 100644
index 0000000..5a40424
--- /dev/null
+++ b/joy/defs.txt
@@ -0,0 +1,115 @@
+-- 1 -
+? dup bool
+&& nulco [nullary [false]] dip branch
+++ 1 +
+|| nulco [nullary] dip [true] branch
+!- 0 >=
+<{} [] swap
+<<{} [] rolldown
+abs dup 0 < [] [neg] branch
+anamorphism [pop []] swap [dip swons] genrec
+app1 grba infrst
+app2 [grba swap grba swap] dip [infrst] cons ii
+app3 3 appN
+appN [grabN] codi map disenstacken
+at drop first
+average [sum] [size] cleave /
+b [i] dip i
+binary unary popd
+ccccons ccons ccons
+ccons cons cons
+clear stack bool [pop stack bool] loop
+cleave fork popdd
+clop cleave popdd
+codi cons dip
+codireco codi reco
+dinfrirst dip infrst
+dipd [dip] codi
+disenstacken ? [uncons ?] loop pop
+down_to_zero [0 >] [dup --] while
+drop [rest] times
+dupd [dup] dip
+dupdd [dup] dipd
+dupdip dupd dip
+dupdipd dup dipd
+enstacken stack [clear] dip
+flatten <{} [concat] step
+fork [i] app2
+fourth rest third
+gcd true [tuck mod dup 0 >] loop pop
+genrec [[genrec] ccccons] nullary swons concat ifte
+grabN <{} [cons] times
+grba [stack popd] dip
+hypot [sqr] ii + sqrt
+ifte [nullary] dipd swap branch
+ii [dip] dupdip i
+infra swons swaack [i] dip swaack
+infrst infra first
+make_generator [codireco] ccons
+mod %
+neg 0 swap -
+not [true] [false] branch
+nulco [nullary] cons
+nullary [stack] dinfrirst
+of swap at
+pam [i] map
+pm [+] [-] clop
+popd [pop] dip
+popdd [pop] dipd
+popop pop pop
+popopop pop popop
+popopd [popop] dip
+popopdd [popop] dipd
+product 1 swap [*] step
+quoted [unit] dip
+range [0 <=] [1 - dup] anamorphism
+range_to_zero unit [down_to_zero] infra
+reco rest cons
+rest [pop] infra
+reverse <{} shunt
+roll> swap swapd
+roll< swapd swap
+rollup roll>
+rolldown roll<
+rrest rest rest
+run <{} infra
+second rest first
+shift uncons [swons] dip
+shunt [swons] step
+size [pop ++] step_zero
+spiral_next [[[abs] ii <=] [[<>] [pop !-] ||] &&] [[!-] [[++]] [[--]] ifte dip] [[pop !-] [--] [++] ifte] ifte
+split_at [drop] [take] clop
+split_list [take reverse] [drop] clop
+sqr dup *
+stackd [stack] dip
+step_zero 0 roll> step
+sum [+] step_zero
+swapd [swap] dip
+swons swap cons
+swoncat swap concat
+tailrec [i] genrec
+take [] roll> [shift] times pop
+ternary binary popd
+third rest second
+tuck dup swapd
+unary nullary popd
+uncons [first] [rest] cleave
+unit [] cons
+unquoted [i] dip
+unswons uncons swap
+while swap nulco dupdipd concat loop
+x dup i
+step [_step0] x
+_step0 _step1 [popopop] [_stept] branch
+_step1 [?] dipd roll<
+_stept [uncons] dipd [dupdipd] dip x
+times [_times0] x
+_times0 _times1 [popopop] [_timest] branch
+_times1 [dup 0 >] dipd roll<
+_timest [[--] dip dupdipd] dip x
+map [_map0] cons [[] [_map?] [_mape]] dip tailrec
+_map? pop bool not
+_mape popd reverse
+_map0 [_map1] dipd _map2
+_map1 stackd shift
+_map2 [infrst] cons dipd roll< swons
diff --git a/setup.py b/setup.py
index bc2a4fe..dcbb273 100755
--- a/setup.py
+++ b/setup.py
@@ -37,6 +37,9 @@ setup(
 	url='https://joypy.osdn.io',
 	license='GPLv3+',
 	packages=['joy', 'joy.utils'],
+        package_data={
+            'joy': ['defs.txt'],
+            },
 	classifiers=[
 		'Development Status :: 4 - Beta',
 		'License :: OSI Approved :: GNU General Public License v3 or later (GPLv3+)',