Span: It is the clear distance between the supports of an arch beam or roof truss.
Rise: It is the vertical distance between the top of the ridge and the wall plate.
Pitch: It is the inclination of the sides of a roof to the horizontal plane. It is expressed either in terms of degrees (angles) or a ratio of rise to span.
Ridge: It is defined as the apex line of the slopping roof. It is thus the apex of the angle formed by the termination of the inclined surfaces at the top of a slope.
Eaves: The lower edge of the inclined roof surface is called eaves. From the lower edge (eaves), the rain water from the roof surface drops down
Hip: It is the ridge formed by the intersection of two sloping surfaces, where the exterior angle is greater than 180o.
Valley: It is a reverse of a hip. It is formed by the intersection of two roof surfaces, making an external angle less than 180o.
Hipped end: It is the sloped triangular surface formed at the end of a roof.
Verge: The edge of a gable, running between the eaves and ridge is known as a verge.
Ridge piece, ridge beam or ridge board: It is the horizontal wooden member, in the form of a beam or board, which is provided at the apex of a roof truss. It supports the common rafters fixed to it.
Common rafters or spans : These are inclined wooden members running from the ridge to the eaves. They are beveled against the ridge beam at the head, and are fixed to the purlins at intermediate point. They support the batten or boarding to support the roof coverings. Depending upon the roof covering material, the rafters are spared 30 to 45 cm centre to centre.
Purlins: These are horizontal wooden or steel members, used to support common rafters of a roof when span is large. Purlins are supported on trusses or walls.
Hip rafters: These are sloping rafters which form the hip of a sloped roof. They run diagonally from the ridge to the corners of the walls to support roof coverings. They receive the purlins and ends of jack rafters.
Valley rafters: These are sloping rafters which run diagonally from the ridge to the eaves for supporting valley gutters. They receive the ends of the purlins and the ends of jack rafters on both sides.
Jack rafters: These are the rafters shorter in length, which run from hip or valley to the eaves.
Eaves board or facia board: It is a wooden plank or board fixed to the feet of the common rafters at the eaves. It is usually 25 mm wide. The ends of lower most roof covering material rest upon it. The eaves gutter, if any, can also be secured against it.
Barge boards: It is a timber board used to hold the common rafter forming verge.
Wall plates: These are long wooden members, which are provided on the top of stone or brick wall, for the purpose of fining the feet of the common rafters. These are embedded from sides and bottom in masonry of the walls, almost at the centre of their thickness. Wall plates actually connect the walls to the roof.
Post plate: This is similar to a wall plate except that they run continuous, parallel to the face of wall, over the tops of the posts, and support rafters at their feet.
Battens: These are thin strips of wood, called scantlings, which are nailed to the rafters for laying the roofing material above.
Boardings: They act similar to battens and are nailed to common rafters to support the roofing material.
Templates: This is a square of rectangular block of stone or concrete placed under a beam or truss, to spread the load over a larger area of the wall.
Cleats: These are short sections of wood or steal (angle iron) which is fixed on the principal rafters of trusses to support the purlins.
Truss: A roof truss is a frame work, usually of triangles, designed to support the roof covering or ceiling over rooms.
They are beveled against the ridge 
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