The Unified Soil Classification System (USCS) is a soil classification system used in engineering and geology to describe the texture and grain size of a soil.
 The classification system can be applied to most unconsolidated materials, and is represented by a two-letter symbol.
 Each letter is described below (with the exception of Pt):
The Baumann Skin Types system is a skin-type classification system defining 16 skin personalities.
 This classification system was developed in 2004 by University of Miami dermatology professor Leslie Baumann, to subdivide research participants into specific phenotypes.
 She assigns binary values to four characteristics, so defining sixteen "skin personalities", or "skin types".
 These have been used in genetic research aimed at identifying the genes that contribute to skin characteristics such as dryness, oiliness, aging, pigmentation and sensitivity.
 The a survey-based typing system combines these individual skin attributes into 16 personalities that allow researchers to improve their ability to identify various skin phenotypes and use that knowledge for patient selection for clinical research trials and to recommend proper skincare ingredients and products.
 The classification system has been adopted by estheticians, dermatologists, consumers and retailers to match cosmeceutical ingredients and skin care products to specific skin types.
 The type assigned is determined by a self-completed questionnaire, marketed as the "Baumann Skin Type Indicator" (BSTI).
The Manual Ability Classification System (MACS) is a medical classification system used to describe how children aged from 4 to 18 years old with cerebral palsy use their hands with objects during activities of daily living, with a focus on the use of both hands together.
 Like the Gross Motor Function Classification System (GMFCS), there are five levels - level I being the least impaired, only finding difficulty in tasks needing speed and accuracy, and level V being the most impaired, not being able to handle objects and having severely limited abilities for even simple actions.
The European Classification (ECLA) is a former patent classification system maintained by the European Patent Office (EPO).
 The ECLA classification system contains 134 000 subdivisions.
 It is mainly an extension of the International Patent Classification system, but sometimes modifies its titles and rules.
 ECLA is used in connection with the indexing system ICO, which serves to identify additional information and aspects that are not covered by the ECLA schemes.
 ECLA has been replaced by the Cooperative Patent Classification (CPC) as of 1 January 2013.
Disability racquetball classification is the medical based classification system developed to allow fair competition between racquetball players with different disability types and against able-bodied competitors.
 Internationally and in Canada, this classification system only allows only wheelchair users to be eligible to compete.
 In contrast, the United States classification system covers wheelchair users and people with vision impairments, with different classes inside these disability types.
The Sawyer and Keeler-Wolf classification system is an evolving system of classification of vegetation types, plant communities, or floristic characterization.
 It was first developed in 1995 by John O. Sawyer and Todd Keeler-Wolf for the California Native Plant Society, in the mission to classify all vegetation in California.
 Particular attention was paid to recognizing rare types that were "lumped" into general categories in previous systems, such as the Munz and Keck classification system, Chetham and Haller classification system, and Holland classification system.
 It uses constantly updated quantitative measurements of both species diversity and cover to define its types.
 It intended to be evolving and to continue to be refined.
Vocal weight refers to the perceived "lightness" or "heaviness" of a singing voice.
 This quality of the voice is one of the major determining factors in voice classification within classical music.
 Lighter voices are often associated with the term "lyric" and are usually brighter and more agile; heavier voices are often associated with the term "dramatic" and are usually powerful, rich, and darker.
 Other voice types like the spinto have a more medium vocal weight.
 Vocal weight can also affect overall vocal agility; heavier voices often have more difficulty maneuvering through florid coloratura passages than their lighter counterparts, as their weight and power compromises agility.
 Likewise, dramatic roles are often written with larger orchestras in mind as dramatic voices can carry more easily over larger ensembles.
A voice type is a particular human singing voice identified as having certain qualities or characteristics of vocal range, vocal weight, tessitura, vocal timbre, and vocal transition points ("passaggio"), such as breaks and lifts within the voice.
 Other considerations are physical characteristics, speech level, scientific testing, and vocal register.
 A singer's voice type is identified by a process known as voice classification, by which the human voice is evaluated and thereby designated into a particular voice type.
 The discipline of voice classification developed within European classical music and is not generally applicable to other forms of singing.
 Voice classification is often used within opera to associate possible roles with potential voices.
 Several different voice classification systems are available to identify voice types, including the German "Fach" system and the choral music system among many others; no system is universally applied or accepted.
The German Fach system (] ; literally "compartment" or "subject of study", here in the sense of "vocal specialization") is a method of classifying singers, primarily opera singers, according to the range, weight, and color of their voices.
 It is used worldwide, but primarily in Europe, especially in German-speaking countries and by repertory opera houses.
A bass ( ) is a type of classical male singing voice and has the lowest vocal range of all voice types.
 According to "The New Grove Dictionary of Opera", a bass is typically classified as having a vocal range extending from around the second E below middle C to the E above middle C (i.e., E–E).
 Its tessitura, or comfortable range, is normally defined by the outermost lines of the bass clef.
 Categories of bass voices vary according to national style and classification system.
 Italians favour subdividing basses into the "basso cantante" (singing bass), "basso buffo" ("funny" bass), or the dramatic "basso profondo" (low bass).
 The American system identifies the bass-baritone, comic bass, lyric bass, and dramatic bass.
 The German "fach" system offers further distinctions: Spielbass (Bassbuffo), Schwerer Spielbass (Schwerer Bassbuffo), Charakterbass (Bassbariton), and Seriöser Bass.
 These classification systems can overlap.
 Rare is the performer who embodies a single "fach" without also touching repertoire from another category.

Question: What is the literal sense of the German voice classification system used to identify voice types?
Answer: vocal specialization