A modular sofa assembly, comprising: a seating module (118; 310) having a seat section and a backrest section, wherein the backrest section includes an upper portion and a lower portion coupled for relative pivotal movement between a folded configuration and an extended configuration that provides a substantially contiguous backrest surface, wherein the upper portion and the lower portion are oriented approximately 90° relative to each other in the folded configuration such that the upper portion is folded against and approximately parallel to the seat section, wherein the lower portion is joined to the seating section at a fixed angle, wherein the upper portion and the lower portion are in line in the extended configuration, wherein the seating module (118; 310) includes a seating side edge surface (122,124) and a plurality of seating connectors, wherein the seating connectors being mounting pins (145; 163; 342) or openings (155, 157; 352, 358) that extend along a first axis at the seating side edge surface (122, 124); and an armrest module (170; 372; 374) including an armrest side edge surface and a plurality of armrest connectors, wherein the armrest connectors being openings (176, 179; 376, 181; 376, 378, 381), with each of the openings of the armrest module (170; 372; 374) being configured for a respective mounting pin (145; 163; 342) of the seating module (118; 310) to slide into said opening, or the armrest connectors being mounting pins (362, 390), with each of the mounting pins of the armrest module (170; 372; 374) being configured to slide into a respective opening of the seating module (118; 310), respectively, with the openings or the mounting pins of the armrest module (170; 372; 374) extending along a second axis at the armrest side edge surface wherein the seating connectors and the armrest connectors are configured such that each of the seating connectors releasably secures a respective armrest connector of the armrest connectors or vice versa, such that the seating module (118; 310) and the armrest module (170; 372; 374) are positioned side-by-side and the seating side edge surface (122,124) abuts against the armrest side edge surface, and wherein an unsecured configuration permits relative movement of the seating module (118; 310) and the armrest module (170; 372; 374) along the first axis in alignment with the second axis. a seating module (118; 310) having a seat section and a backrest section, wherein the backrest section includes an upper portion and a lower portion coupled for relative pivotal movement between a folded configuration and an extended configuration that provides a substantially contiguous backrest surface, wherein the upper portion and the lower portion are oriented approximately 90° relative to each other in the folded configuration such that the upper portion is folded against and approximately parallel to the seat section, wherein the lower portion is joined to the seating section at a fixed angle, wherein the upper portion and the lower portion are in line in the extended configuration, wherein the seating module (118; 310) includes a seating side edge surface (122,124) and a plurality of seating connectors, wherein the seating connectors being mounting pins (145; 163; 342) or openings (155, 157; 352, 358) that extend along a first axis at the seating side edge surface (122, 124); and an armrest module (170; 372; 374) including an armrest side edge surface and a plurality of armrest connectors, wherein the armrest connectors being openings (176, 179; 376, 181; 376, 378, 381), with each of the openings of the armrest module (170; 372; 374) being configured for a respective mounting pin (145; 163; 342) of the seating module (118; 310) to slide into said opening, or the armrest connectors being mounting pins (362, 390), with each of the mounting pins of the armrest module (170; 372; 374) being configured to slide into a respective opening of the seating module (118; 310), respectively, with the openings or the mounting pins of the armrest module (170; 372; 374) extending along a second axis at the armrest side edge surface wherein the seating connectors and the armrest connectors are configured such that each of the seating connectors releasably secures a respective armrest connector of the armrest connectors or vice versa, such that the seating module (118; 310) and the armrest module (170; 372; 374) are positioned side-by-side and the seating side edge surface (122,124) abuts against the armrest side edge surface, and wherein an unsecured configuration permits relative movement of the seating module (118; 310) and the armrest module (170; 372; 374) along the first axis in alignment with the second axis.