Interlock, Smooth, Jersey, Knit: What the Difference Actually Is
May 20, 2026 — Mercer St.
When a garment is described as "knitted," that word covers a wide range of structures. A fine cotton T-shirt and a chunky wool sweater are both knitted. So is a pair of socks and a close-fitting innerwear piece. What makes them different is not just the fibre — it is the structure of the knit itself.
This note explains the four structures most relevant to Mercer St. pieces: jersey, interlock, smooth knit, and knitwear. Understanding the difference helps explain why the same material can feel and behave so differently from one garment to the next.
In this note
- How knitted fabric is made — the shared foundation
- What jersey is and how it behaves
- What interlock is and how it differs from jersey
- What smooth knit means — and how it is achieved
- What knitwear refers to as a category
- A comparison of the four structures
How knitted fabric is made
All knitted fabric is formed by interlocking loops of yarn. Unlike woven fabric — where threads cross at right angles — knitted fabric is made from a continuous yarn that forms a series of connected loops. This loop structure is what gives knitted fabric its stretch and recovery.
The two basic stitches in knitting are the knit stitch (a smooth V-shape on the face) and the purl stitch (a horizontal bump on the face). Different arrangements of these stitches produce different structures with different properties.
Most jersey, interlock, and smooth knit fabrics are produced on circular knitting machines, which produce fabric as a continuous tube. The gauge of the machine — needles per inch of circumference — determines how fine or coarse the resulting fabric is.
Jersey
Jersey is the most common knitted fabric structure. It is a single-knit construction: formed by a single set of needles, with knit stitches on the face and purl stitches on the back.
- Smooth face, slightly textured reverse
- High horizontal stretch, moderate vertical stretch
- Tendency to curl at cut edges before finishing
- Relatively lightweight for its gauge
- Fluid drape
Jersey is the standard structure for T-shirts. Fine-gauge jersey — produced on a high-needle-count machine with a fine yarn — has a closer, smoother surface than coarser jersey. One property worth noting: fine jersey can be semi-transparent in lighter colours, particularly in direct light. This is a structural property, not a defect.
Interlock
Interlock is a double-knit construction. It is produced on a machine with two sets of needles arranged alternately, each set knitting into the other. The result is a fabric with a smooth face on both sides.
- Smooth on both face and reverse
- More stable than jersey — does not curl at edges
- Less horizontal stretch than jersey
- Slightly firmer, more substantial hand
- Heavier per unit area than jersey at the same gauge (uses more yarn)
Interlock is used for fine innerwear and base layers, where a smooth surface on both sides is desirable and dimensional stability matters.
Mercer Note
The Materica Black T-Shirt uses an interlock construction rather than jersey. The difference is in the stability and surface character: interlock sits more evenly against the skin, holds its shape better after washing, and does not have the curling tendency of single-knit jersey.
Smooth knit
"Smooth knit" is not a single technical term. It describes fabrics engineered to produce a very even, flat surface — with minimal visible stitch structure and a close, refined hand. This can be achieved through several means:
- Very fine gauge and fine yarn (increasing loop density)
- Specific stitch variations that reduce surface texture
- Finishing processes such as calendering (passing through heated rollers)
Smooth knit fabrics are typically used for fine innerwear, base layers, and close-fitting pieces where the priority is a clean surface against the skin. The term describes the result rather than a single construction method.
Knitwear
When a garment is described as a "knit" — a knit top, a knit sweater, knitwear — it usually refers to a garment produced differently from jersey or interlock. Rather than being cut from a length of circular-knit fabric, knitwear is typically produced on a flatbed knitting machine, where panels or whole garments are shaped as they are knitted.
- Visible stitch structure — the stitch is part of the aesthetic
- Typically coarser gauge and heavier yarn than jersey or interlock
- Shaped during knitting rather than cut and sewn
- Varied surface textures: plain knit (stocking stitch), rib, cable, moss stitch, and many others
Comparison
| Structure | Construction | Surface | Stretch | Typical use |
|---|---|---|---|---|
| Jersey | Single-knit, circular | Smooth face, textured back | High horizontal | T-shirts, lightweight tops |
| Interlock | Double-knit, circular | Smooth both sides | Moderate horizontal | Innerwear, base layers, structured tops |
| Smooth knit | Varies (fine gauge / finished) | Very smooth, minimal texture | Varies | Fine innerwear, close-fit pieces |
| Knitwear | Flatbed, shaped | Visible stitch structure | Varies by stitch | Sweaters, knitwear pieces |
The knit structure is not decorative. It determines how a garment behaves, holds its shape, and sits against the skin.
What to look for
- Is the knit structure identified on the product page?
- Is the gauge or yarn count mentioned?
- Does the product description explain why a particular structure was chosen?
What this means for Mercer St.
The knit structure for each Mercer St. piece is noted on the product page. Where interlock is used rather than jersey — as in the Materica T-Shirt — this reflects a specific decision about stability, surface character, and behaviour over time. [VERIFY: confirm knit structure for each piece with supplier before publishing any product-specific claims]