Blade

A blade is the flat cutting part of a tool or weapon, typically thin and rigid, with a sharp edge that can cut or slice through material. The term is used for blades in knives, razors, swords, and various cutting implements. In biology and engineering, other senses exist for the term blade.

In tools and weapons, blades are manufactured from steel alloys such as carbon steel or stainless steel, and may be hardened or tempered to create a sharper edge. Edge geometry, grind type, and bevel angle determine cutting performance. Blades require regular maintenance, including sharpening and honing; improper sharpening can create uneven edges or chipping. Some blades are disposable, such as razor blades.

In botany, the blade is the broad, flattened part of a leaf, also called the leaf blade. It is attached to the leaf stalk (petiole) in many plants. Leaf blades vary in shape, size, and venation and are specialized for photosynthesis, gas exchange, and water transport.

In engineering, blade refers to aerodynamic surfaces that rotate or move through a fluid, such as turbine blades in jet engines and steam turbines, or propeller and fan blades. These blades are usually made of high-strength alloys and may incorporate coatings or cooling systems to withstand high temperatures and stresses. The design focuses on airflow, lift, and structural integrity.