Annulus: The space between two concentric pipes (e.g., drill pipe and casing, or casing and the borehole wall) or between the drill string and the borehole wall. This space is often used for the circulation of drilling fluid.

BHA (Bottom Hole Assembly): The lower part of the drill string, consisting of the drill bit, drill collars, stabilizers, and other drilling tools, designed to provide weight on bit and control the direction of the wellbore.

Bit: The cutting tool at the end of the drill string that grinds, crushes, or cuts the rock to create the borehole. Different bit types are used for various rock formations.

Borehole: The actual hole drilled into the earth. Also referred to as a wellbore.

Borehole Log (or Well Log): A continuous record of geological, geophysical, or drilling parameters measured in a borehole, used to characterize the subsurface formations.

Borehole Wall: The side of the drilled hole.

BPM (Bits Per Minute): A measure of the drilling rate, indicating how many bits are used per minute. (Less common in general drilling, more specific to certain drilling techniques or rock types).

Breakthrough: The point at which the drill bit penetrates a new formation or reaches a target depth.

Casing: Steel pipe that is run into the borehole and cemented in place to prevent the hole from caving in, to isolate different fluid-bearing formations, and to provide a conduit for production.

Cementing: The process of pumping cement slurry down the casing and into the annulus to bond the casing to the formation and seal off zones.

Collar (Drill Collar): Heavy, thick-walled steel pipes that are part of the BHA, providing weight on the bit and rigidity to the drill string.

Core: A cylindrical sample of rock or soil obtained from the borehole, used for geological analysis.

Core Barrel: A device used to cut and retrieve core samples from the borehole.

Cuttings: Fragments of rock dislodged by the drill bit and brought to the surface by the drilling fluid. These are analyzed by geologists to understand the subsurface geology.

Deviation: The intentional or unintentional departure of a borehole from a true vertical path.

Directional Drilling: The practice of drilling non-vertical wells to reach targets that are not directly beneath the rig, or to optimize reservoir drainage.

Downhole: Refers to anything located within the borehole.

Draw works: The hoisting mechanism on a drilling rig that spools the drilling line and raises and lowers the drill string.

Drill Bit: A rotary cutting tool used with a power drill to bore precise, circular holes into various materials. The right bit depends on the material you need to drill 

Drill Pipe: Heavy, seamless steel pipe that makes up the majority of the drill string, connecting the surface equipment to the drill bit and allowing for the circulation of drilling fluid.

Drill String: The entire assembly of drill pipe, drill collars, and the BHA that transmits rotational power from the rig to the drill bit.

Drilling Fluid (Mud): A specially engineered fluid circulated down the drill string and up the annulus to cool and lubricate the bit, carry cuttings to the surface, and maintain hydrostatic pressure to prevent formation fluids from entering the wellbore.

Drilling Rig: The complete machinery and equipment used to drill a borehole.

Formation: A body of rock or sediment with distinctive characteristics that allow it to be mapped and described.

Formation Pressure: The pressure of fluids (water, oil, gas) within the pore spaces of a rock formation.

Geological Survey: The process of investigating and mapping the geology of an area, often preceding drilling operations.

Geophysical Logging: The process of acquiring continuous measurements of physical properties of formations in a borehole using specialized tools.

Grout: A fluid mixture (often cement-based) used to fill voids, seal boreholes, or provide structural support.