1. BASIC NOMENCLATURE OF FOLD
Cylindrical Fold: If every surface in the fold structure contains a line parallel to the hinge line, i.e., a fold generated by a straight line moving parallel to itself in space.

2. BASIC NOMENCLATURE OF FOLD
Noncylindrical Fold: The folded surface do not all contain a line parallel to the hinge line, i.e., a fold cannot be generated by a straight line moving parallel to itself in space.

3. BASIC NOMENCLATURE OF FOLD
Conical Fold: Some noncylinderical folds have their surfaces arranged so as to form part of a cone and are known as conical folds.

4. BASIC NOMENCLATURE OF FOLD
Fold Orientation: The orientation of a fold is completely defined by the direction of closure, and the attitude of the hinge line and hinge surface.
There are three terms which are used to describe the direction of closure.
1. ANTIFORM:
2. SYNFORM:
3. NEUTRAL FOLD:

5. BASIC NOMENCLATURE OF FOLD
Fold Orientation: The orientation of a fold is completely defined by the direction of closure, and the attitude of the hinge line and hinge surface.
There are three terms which are used to describe the direction of closure.
1. ANTIFORM: An antiform is a fold which closes upward.

6. BASIC NOMENCLATURE OF FOLD
Fold Orientation: The orientation of a fold is completely defined by the direction of closure, and the attitude of the hinge line and hinge surface.
There are three terms which are used to describe the direction of closure.
2. SYNFORM: A synform is a fold which closes downward.

7. BASIC NOMENCLATURE OF FOLD
Fold Orientation: The orientation of a fold is completely defined by the direction of closure, and the attitude of the hinge line and hinge surface.
There are three terms which are used to describe the direction of closure.
3. NEUTRAL FOLD: A fold which closes sideways, or defined more strictly, it is a fold with a hinge pitching at between 800 and 900 on the hinge surface.

8. BASIC NOMENCLATURE OF FOLD
Anticline: A fold, generally convex upward whose core contains the stratigraphically older rocks. In other words, an anticline is a fold that is convex in the direction of the youngest beds in the folded sequence and the fold limbs dip away from each other.
Syncline: A fold of which the core contains the stratigraphically younger rocks; it is generally concave upward and the fold limbs dip towards each other.

9. Anticlines and Synclines
BASIC NOMENCLATURE OF FOLD

10. BASIC NOMENCLATURE OF FOLD
Synformal Anticline: A synclinal fold in which the core contains the stratigraphically older rocks; i.e., it is the inverted form of an anticline.
Antiformal Syncline: An anticlinal fold in which the core contains the younger rocks; i.e., it is the inverted form of syncline.

11. BASIC NOMENCLATURE OF FOLD
Anticlinorium: A major anticline that is composed of many smaller folds is called an anticlinorium. The term is restricted to large folds that are at least several miles across.
Synclinorium: A synclinorium is a large syncline composed of many smaller folds; it should be at least several miles across.