Refers to railroad track spacing that is wider than the "standard gauge" of 4 feet 8-1/2 inches (143.5cm). Russian railroad use this.

Indicates that the model or layout is not built to a particular prototype, but rather free-form as the modeler saw fit.

Same as "scale", indicating the relative size of a model compared to the real world object. Generally "gauge" is used in the larger models, whereas scale seems to refer more to accurate models. However, both words can be used interchangeably in the hobby magazines and books.

Pronounced "age-ooh", which stands for "half-O", or half O-scale. It specifically refers to models that are scaled to "1:87", or 1/87th of the real world object being modeled. O-scale came before HO, hence is heritage. This is by far the most popular model railroading scale used around the world. It has a nice balance between being able to get a nice-sized model railroad in available space, having good visibility of the models, while still being able to model scenery.

Kitbashing is a modeling term used to indicate that a particular model kit (as bought in the store) was not quite built to the kit manufacturer's instructions. A bit of modeler's license was used to make the final model different from the intended, typically by building it differently, or adding parts from other kits, or even adding scratchbuilt parts. Generally after the modeler has built a few kits as per the instructions, he or she starts seeing that same model on other modelers' layouts. Kitbashing is done to add some creativity or individualism to the finished model. Also, a modeler may do some kitbashing to make the model match a prototype object better.

N-scale refers to models that are scaled down 1/160th of the real world object, or "1:160". The letter "N" has its history in the word "nine" in German, "Neun", which refers to the 9mm spacing between the tracks in that scale. The scale was invented in Germany, and spread to the United States after World War II when American GI's brought models home. This is the second most popular model railroading scale (after HO). It provides a balance between being able to model large railroading scenery in relatively confined spaces. In larger spaces, such as whole basements, vast scenery can be modeled in this scale.

Both a prototype and a modeling term used to indicate the spacing between the tracks as being smaller than "standard gauge". Popular narrow gauge spacings are 3 feet and 2-1/2 feet.

O-scale represents models that are 1:48 scale, or 1/48th the size of the real world. The U.K. uses 1:43 for the same definition of O-scale. The popular Lionel brand of model trains are O-scale.

Typically refers to the model or layout that the modeler built in free-form, but yet applied some amount of prototypical realism. For example, since all model railroaders have only limited amount of space to model a railroad, selective compression has to take place. The track and equipment and even some of the structures may be exact replicas of the real world, distances between towns and buildings may have to be shortened to allow them to fit in the given space. Perhaps a model of the building in town A is placed in the layout's town B because it fits better, space-wise. These are all examples of a proto-freelance layout.

A hobby term that refers to the real world, or the actual locomotive, structure, or scenery. Also "prototypical".

This abbreviation stands for "Railway Post Office". It was basically a passenger car built to house a fully-functional U.S. Post Office. Mail was sorted while in transit. Mail was delivered and picked up at all the towns along the route, sometimes without stopping.

S-scale represents models that are 1:64 scale, or 1/64th the size of the real world. Originally the scale was dominated by "American Flyer", which is more of a toy-train model. However, there is a small, but growing, group of individuals and clubs that modeling in true scale, just like HO and N.

Same as "gauge", indicating the relative size of a model compared to the real world object. For example, "1:160" indicates a scale where one unit of measure in the physical model matches 160 units of measure in the real world object being modeled. Rather than constantly refering to numerical scales, the hobby uses terms such as "n-scale" or "HO scale" to refer to a particular scale.

Landscape, such as mountains, fields, rivers, lakes, trees, etc.

To scratchbuild means to make something from scratch. This typically involves starting from raw materials. For example, to build a model of his or her house, a modeler may start with a plan and gather up all the individual pieces of scale wood that are necessary. Each piece of wood is glued to another making up walls. Several walls are glued together to make up a floor, or level. Finally, a roof is assembled and attached to finish the model. This model is said to be scratchbuilt. Popular materials are scale strip or sheet wood, scale strip or sheet styrene (a plastic), plaster, foamboard, cardboard, and paper.

Refers to the spacing between the tracks of U.S. railroads (also used in some other countries). The standard is 4 feet, 8-1/2 inches (143.5cm) between the rails. Gauges narrowing than this are called "narrow gauge" and gauges wider than this are called "broad gauge".

Buildings, homes, bridges, industrial buildings, etc.

A nickname for EMD's SD45T-2's because they were a solution to the problem with diesel locomotives overheating when there wasn't enough fresh air coming into the radiator air intakes of the engines.