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diff --git a/src/main/java/org/apache/commons/math3/geometry/euclidean/threed/RotationConvention.java b/src/main/java/org/apache/commons/math3/geometry/euclidean/threed/RotationConvention.java
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+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.commons.math3.geometry.euclidean.threed;
+
+/**
+ * This enumerates is used to differentiate the semantics of a rotation.
+ * @see Rotation
+ * @since 3.6
+ */
+public enum RotationConvention {
+
+    /** Constant for rotation that have the semantics of a vector operator.
+     * <p>
+     * According to this convention, the rotation moves vectors with respect
+     * to a fixed reference frame.
+     * </p>
+     * <p>
+     * This means that if we define rotation r is a 90 degrees rotation around
+     * the Z axis, the image of vector {@link Vector3D#PLUS_I} would be
+     * {@link Vector3D#PLUS_J}, the image of vector {@link Vector3D#PLUS_J}
+     * would be {@link Vector3D#MINUS_I}, the image of vector {@link Vector3D#PLUS_K}
+     * would be {@link Vector3D#PLUS_K}, and the image of vector with coordinates (1, 2, 3)
+     * would be vector (-2, 1, 3). This means that the vector rotates counterclockwise.
+     * </p>
+     * <p>
+     * This convention was the only one supported by Apache Commons Math up to version 3.5.
+     * </p>
+     * <p>
+     * The difference with {@link #FRAME_TRANSFORM} is only the semantics of the sign
+     * of the angle. It is always possible to create or use a rotation using either
+     * convention to really represent a rotation that would have been best created or
+     * used with the other convention, by changing accordingly the sign of the
+     * rotation angle. This is how things were done up to version 3.5.
+     * </p>
+     */
+    VECTOR_OPERATOR,
+
+    /** Constant for rotation that have the semantics of a frame conversion.
+     * <p>
+     * According to this convention, the rotation considered vectors to be fixed,
+     * but their coordinates change as they are converted from an initial frame to
+     * a destination frame rotated with respect to the initial frame.
+     * </p>
+     * <p>
+     * This means that if we define rotation r is a 90 degrees rotation around
+     * the Z axis, the image of vector {@link Vector3D#PLUS_I} would be
+     * {@link Vector3D#MINUS_J}, the image of vector {@link Vector3D#PLUS_J}
+     * would be {@link Vector3D#PLUS_I}, the image of vector {@link Vector3D#PLUS_K}
+     * would be {@link Vector3D#PLUS_K}, and the image of vector with coordinates (1, 2, 3)
+     * would be vector (2, -1, 3). This means that the coordinates of the vector rotates
+     * clockwise, because they are expressed with respect to a destination frame that is rotated
+     * counterclockwise.
+     * </p>
+     * <p>
+     * The difference with {@link #VECTOR_OPERATOR} is only the semantics of the sign
+     * of the angle. It is always possible to create or use a rotation using either
+     * convention to really represent a rotation that would have been best created or
+     * used with the other convention, by changing accordingly the sign of the
+     * rotation angle. This is how things were done up to version 3.5.
+     * </p>
+     */
+    FRAME_TRANSFORM;
+
+}