diff --git a/exputil/localmpi.cc b/exputil/localmpi.cc
index 987230175..b0ddc8708 100644
--- a/exputil/localmpi.cc
+++ b/exputil/localmpi.cc
@@ -11,9 +11,9 @@
 //
 // MPI variables
 //
-MPI_Comm MPI_COMM_SLAVE;
-MPI_Group world_group, slave_group;
-int numprocs=1, slaves, myid=0, proc_namelen;
+MPI_Comm MPI_COMM_WORKER;
+MPI_Group world_group, worker_group;
+int numprocs=1, workers, myid=0, proc_namelen;
 char processor_name[MPI_MAX_PROCESSOR_NAME];
 std::ofstream mpi_debug;
 
@@ -29,18 +29,18 @@ void local_init_mpi(int argc, char **argv)
   MPI_Get_processor_name(processor_name, &proc_namelen);
 
   //=========================
-  // Make SLAVE communicator
+  // Make WORKER communicator
   //=========================
 
-  slaves = numprocs - 1;
+  workers = numprocs - 1;
 
-  if (slaves) {
+  if (workers) {
     MPI_Comm_group(MPI_COMM_WORLD, &world_group);
-    std::vector<int> nslaves (slaves);
+    std::vector<int> nworkers (workers);
 
-    for (int n=1; n<numprocs; n++) nslaves[n-1] = n;
-    MPI_Group_incl(world_group, slaves, &nslaves[0], &slave_group);
-    MPI_Comm_create(MPI_COMM_WORLD, slave_group, &MPI_COMM_SLAVE);
+    for (int n=1; n<numprocs; n++) nworkers[n-1] = n;
+    MPI_Group_incl(world_group, workers, &nworkers[0], &worker_group);
+    MPI_Comm_create(MPI_COMM_WORLD, worker_group, &MPI_COMM_WORKER);
   }
 
   //=========================
@@ -68,7 +68,7 @@ void local_init_mpi(int argc, char **argv)
 		<< " | " << std::setw(8)  << getpid();
       
       if (n) {
-	int m; MPI_Group_rank ( slave_group, &m );
+	int m; MPI_Group_rank ( worker_group, &m );
 	std::cout << " | " << std::setw(10) << "WORKER " << m << std::endl;
       } else {
 	std::cout << " | " << std::setw(10) << "ROOT" << std::endl;
diff --git a/include/localmpi.H b/include/localmpi.H
index e6fad4967..b61766b2c 100644
--- a/include/localmpi.H
+++ b/include/localmpi.H
@@ -12,9 +12,9 @@
 #include <iomanip>
 #include <string>
 
-extern MPI_Comm MPI_COMM_SLAVE;
-extern MPI_Group world_group, slave_group;
-extern int numprocs, slaves, myid, proc_namelen;
+extern MPI_Comm MPI_COMM_WORKER;
+extern MPI_Group world_group, worker_group;
+extern int numprocs, workers, myid, proc_namelen;
 extern char processor_name[MPI_MAX_PROCESSOR_NAME];
 extern std::ofstream mpi_debug;
 
diff --git a/src/Component.cc b/src/Component.cc
index 47fe2901c..609c1b07e 100644
--- a/src/Component.cc
+++ b/src/Component.cc
@@ -1768,7 +1768,7 @@ void Component::read_bodies_and_distribute_binary_spl(istream *in)
       in->read((char*)&number, sizeof(int));
     } catch (...) {
       std::ostringstream sout;
-      sout << "Error reading magic info and file count from master";
+      sout << "Error reading magic info and file count from root";
       throw GenericError(sout.str(), __FILE__, __LINE__, 1010, true);
     }
 
@@ -2116,7 +2116,7 @@ PartPtr * Component::get_particles(int* number)
 	for (auto it=itb; it!=ite; it++) pbuf[icount++] = it->second;
 
 #ifdef DEBUG
-	std::cout << "get_particles: master loaded " 
+	std::cout << "get_particles: root loaded " 
 		  << icount << " of its own particles"
 		  << ", beg=" << beg << ", iend=" << end
 		  << ", dist=" << std::distance(itb, ite)
@@ -2133,7 +2133,7 @@ PartPtr * Component::get_particles(int* number)
       while (PartPtr part=pf->RecvParticle()) pbuf[icount++] = part;
 #ifdef DEBUG
       std::cout << "Process " << myid 
-	   << ": received " << icount << " particles from Slave " << node
+	   << ": received " << icount << " particles from Worker " << node
 		<< ", expected " << number << ", total=" << totals[node]
 		<< std::endl << std::flush;
 #endif    
@@ -2145,7 +2145,7 @@ PartPtr * Component::get_particles(int* number)
       curcount++;
       counter++;
     }
-				// Nodes send particles to master
+				// Nodes send particles to root
   } else if (myid == node) {
       
     auto itb = particles.begin();
@@ -2163,7 +2163,7 @@ PartPtr * Component::get_particles(int* number)
 
 #ifdef DEBUG
       std::cout << "Process " << myid 
-		<< ": sent " << icount << " particles from Slave " << node
+		<< ": sent " << icount << " particles from Worker " << node
 		<< std::endl << std::flush;
 #endif    
   }
@@ -3353,7 +3353,7 @@ int Component::round_up(double dnumb)
 
 void Component::setup_distribution(void)
 {
-				// Needed for both master and slaves
+				// Needed for both root and workers
   nbodies_index = vector<unsigned int>(numprocs);
   nbodies_table = vector<unsigned int>(numprocs);
 
diff --git a/src/Orient.cc b/src/Orient.cc
index 2fa2f9bb1..676e40792 100644
--- a/src/Orient.cc
+++ b/src/Orient.cc
@@ -76,7 +76,7 @@ Orient::Orient(int n, int nwant, unsigned Oflg, unsigned Cflg,
   int in_ok;
   std::vector<double> in1(4), in2(4);
 
-  if (myid==0) {		// Master does the reading
+  if (myid==0) {		// Root does the reading
 
     ifstream in(logfile.c_str());
     
@@ -115,7 +115,7 @@ Orient::Orient(int n, int nwant, unsigned Oflg, unsigned Cflg,
       double time;
       int tused;
 
-      in_ok = 1;		// Signal slave: OK
+      in_ok = 1;		// Signal worker: OK
 	
       MPI_Bcast(&in_ok, 1, MPI_INT, 0, MPI_COMM_WORLD);
 
@@ -176,12 +176,12 @@ Orient::Orient(int n, int nwant, unsigned Oflg, unsigned Cflg,
       if (restart)
       cout << "  -- Orient: cached time=" << time << "  Ecurr= " << Ecurr << endl;
 
-      cout << "  -- Orient: axis master (cache size=" << sumsA.size() << "): " 
+      cout << "  -- Orient: axis root (cache size=" << sumsA.size() << "): " 
 	   << axis[0] << ", "
 	   << axis[1] << ", "
 	   << axis[2] << endl;
       
-      cout << "  -- Orient: center master (cache size=" << sumsC.size() << "): " 
+      cout << "  -- Orient: center root (cache size=" << sumsC.size() << "): " 
 	   << center[0] << ", "
 	   << center[1] << ", "
 	   << center[2] << endl;
@@ -212,7 +212,7 @@ Orient::Orient(int n, int nwant, unsigned Oflg, unsigned Cflg,
 
     } else {
 	
-      in_ok = 0;		// Signal slave: NO VALUES
+      in_ok = 0;		// Signal worker: NO VALUES
 	
       MPI_Bcast(&in_ok, 1, MPI_INT, 0, MPI_COMM_WORLD);
 
@@ -261,7 +261,7 @@ Orient::Orient(int n, int nwant, unsigned Oflg, unsigned Cflg,
     
   } else {
 
-				// Get state from Master
+				// Get state from Root
 
     MPI_Bcast(&in_ok, 1, MPI_INT, 0, MPI_COMM_WORLD);
 
diff --git a/src/end.cc b/src/end.cc
index 5b0577e7e..2f7c0afb9 100644
--- a/src/end.cc
+++ b/src/end.cc
@@ -26,13 +26,13 @@ void clean_up(void)
 		     << "Process " << setw(4) << right << myid 
 		     << " on " << processor_name
 		     << "   pid=" << getpid()
-		     << "   MASTER NODE\t Exiting EXP\n";
+		     << "   ROOT NODE\t Exiting EXP\n";
   MPI_Barrier(MPI_COMM_WORLD);
   for (int j=1; j<numprocs; j++) {
     if (myid==j) cerr << "Process " << setw(4) << right << myid 
 		      << " on " << processor_name
 		      << "   pid=" << getpid()
-		      << "   rank in SLAVE: " << j << "\t Exiting EXP\n";
+		      << "   rank in WORKER: " << j << "\t Exiting EXP\n";
     MPI_Barrier(MPI_COMM_WORLD);
   }
 
diff --git a/src/expand.cc b/src/expand.cc
index 3f1abd4fd..fb9357244 100644
--- a/src/expand.cc
+++ b/src/expand.cc
@@ -173,8 +173,8 @@ main(int argc, char** argv)
   char hdbuffer[hdbufsize];
   bool final_cmd = false;
 
-  int *nslaves, n, retdir, retdir0;
-  MPI_Group world_group, slave_group;
+  int *nworkers, n, retdir, retdir0;
+  MPI_Group world_group, worker_group;
   MPI_Errhandler errhandler;
 
   //===================
@@ -192,23 +192,23 @@ main(int argc, char** argv)
     MPI_Comm_set_errhandler(MPI_COMM_WORLD, errhandler);
   }
 
-				// Make SLAVE group 
-#ifdef SLAVE_GROUP
-  slaves = numprocs - 1;
+				// Make WORKER group 
+#ifdef WORKER_GROUP
+  workers = numprocs - 1;
   MPI_Comm_group(MPI_COMM_WORLD, &world_group);
-  nslaves = new int [slaves];
-  if (!nslaves) {
-    cerr << "main: problem allocating <nslaves>\n";
+  nworkers = new int [workers];
+  if (!nworkers) {
+    cerr << "main: problem allocating <nworkers>\n";
     MPI_Finalize();
     exit(10);
   }
-  for (n=1; n<numprocs; n++) nslaves[n-1] = n;
-  MPI_Group_incl(world_group, slaves, nslaves, &slave_group);
-  MPI_Comm_create(MPI_COMM_WORLD, slave_group, &MPI_COMM_SLAVE);
-  delete [] nslaves;
+  for (n=1; n<numprocs; n++) nworkers[n-1] = n;
+  MPI_Group_incl(world_group, workers, nworkers, &worker_group);
+  MPI_Comm_create(MPI_COMM_WORLD, worker_group, &MPI_COMM_WORKER);
+  delete [] nworkers;
 
   // Debug id 
-  MPI_Group_rank ( slave_group, &n );
+  MPI_Group_rank ( worker_group, &n );
   if (myid==0)  cerr << setfill('-') << setw(70) << "-" << endl
 		     << setfill(' ')
 		     << "Process " << setw(4) << right << myid 
@@ -222,7 +222,7 @@ main(int argc, char** argv)
     if (myid==j) cerr << "Process " << setw(4) << right << myid 
 		      << " on " << processor_name
 		      << "   pid=" << getpid()
-		      << "   rank in SLAVE: " << j << "\t Ready to go!\n";
+		      << "   rank in WORKER: " << j << "\t Ready to go!\n";
     MPI_Barrier(MPI_COMM_WORLD);
   }
   if (myid==0)  cerr << setfill('-') << setw(70) << "-" << endl
diff --git a/src/global.H b/src/global.H
index a54fb23ba..d98aa6ec6 100644
--- a/src/global.H
+++ b/src/global.H
@@ -246,8 +246,8 @@ extern int dump_signal0;
 //! Used to flag separate behavior on inintialization (unused)
 extern int is_init;
 
-//! Internally defined slave communicator
-extern MPI_Comm MPI_COMM_SLAVE;
+//! Internally defined worker communicator
+extern MPI_Comm MPI_COMM_WORKER;
 
 //! List of host names and ranks
 extern std::map<std::string, std::vector<int> > nameMap;
diff --git a/utils/SL/cyltest.cc b/utils/SL/cyltest.cc
index 257082b55..4ee092f0b 100644
--- a/utils/SL/cyltest.cc
+++ b/utils/SL/cyltest.cc
@@ -223,7 +223,7 @@ int main(int argc, char** argv)
   //                                                                    |
   // Turn on diagnostic output in SL creation---------------------------+
 
-				// Slaves exit
+				// Workers exit
   if (use_mpi && myid>0) {
     MPI_Finalize();
     exit(0);
diff --git a/utils/SL/qtest.cc b/utils/SL/qtest.cc
index 6547c23e4..1a3e1cf40 100644
--- a/utils/SL/qtest.cc
+++ b/utils/SL/qtest.cc
@@ -104,7 +104,7 @@ int main(int argc, char** argv)
   //                                                                          |
   // Turn on diagnostic output in SL creation---------------------------------+
 
-				// Slaves exit
+				// Workers exit
   if (use_mpi && myid>0) {
     MPI_Finalize();
     exit(0);
diff --git a/utils/SL/slcheck.cc b/utils/SL/slcheck.cc
index 85a1cea9c..4a28596e8 100644
--- a/utils/SL/slcheck.cc
+++ b/utils/SL/slcheck.cc
@@ -124,7 +124,7 @@ int main(int argc, char** argv)
     }
     bad = true;
   }
-				// Slaves exit
+				// Workers exit
   if (use_mpi && myid>0) {
     MPI_Finalize();
     exit(0);
diff --git a/utils/Test/test_barrier.cc b/utils/Test/test_barrier.cc
index 6635aa172..932b293ba 100644
--- a/utils/Test/test_barrier.cc
+++ b/utils/Test/test_barrier.cc
@@ -56,7 +56,7 @@ int main(int argc, char **argv)
   // MPI preliminaries
   //--------------------------------------------------
 
-  int numprocs, slaves, myid, proc_namelen;
+  int numprocs, myid, proc_namelen;
   char processor_name[MPI_MAX_PROCESSOR_NAME];
 
   MPI_Init(&argc, &argv);