Philatelists have observed the development of mail transport by air from its beginning, and all aspects of airmail services have been extensively studied and documented by specialists.

Philatelists have observed the development of mail transport by air from its beginning, and all aspects of airmail service have been extensively studied and documented by specialists.

In addition, Caillebotte used his wealth to fund a variety of hobbies for which he was quite passionate, including stamp collecting ( his name was inscribed in the Roll of Distinguished Philatelists, and his collection is now in the British Library ), orchid horticulture, yacht building, and even textile design ( the women in his paintings Madame Boissière Knitting, 1877, and Portrait of Madame Caillebotte, 1877, may be working on patterns created by Caillebotte ).

Philatelists observe the development of mail transport by air from its beginning, and most aspects of airmail service have been extensively studied and documented by specialists, some of which are individually listed.

Philatelists ' traditional method of identifying postage stamps uniquely has long been to number each country's stamps consecutively ; Norway # 1 is the 4-skilling blue stamp issued in 1855, and so forth.

Philatelists typically identify more types of stamps than do the governments issuing them.

Philatelists count changes in these marginal inscriptions as distinct types of stamps.

Loki is particularly difficult to classify ; he is usually called an áss, but is really of jǫtunn origin, and is nevertheless also addressed as álfr.

Ancient writers usually classify the Teutons as " Germanic " and the Helvetii as " Gallic ," but these ethnic attributions are debatable.

Although traditionally considered one of seven colors of the rainbow or the optical spectrum, modern color scientists do not usually recognize indigo as a separate division and generally classify wavelengths shorter than about 450 nm as violet.

In biology, phenetics (), also known as taximetrics, is an attempt to classify organisms based on overall similarity, usually in morphology or other observable traits, regardless of their phylogeny or evolutionary relation.

It is common to classify such engines by the number and alignment of cylinders and total volume of displacement of gas by the pistons moving in the cylinders usually measured in cubic centimetres ( cm³ or cc ) or litres ( l ) or ( L ) ( US: liter ).

The basic goal is to find algebraic invariants that classify topological spaces up to homeomorphism, though usually most classify up to homotopy equivalence.

Moral rights are usually considered to be a matter for the national laws of the Member States, although some countries classify some of the above rights, especially the right of communication to the public, among the moral rights of the author rather than under his rights of exploitation.

The 130 volumes ( i. e. scrolls, now usually called " chapters ") of the text classify information into several categories:

Historically, the description of a bacterium lacking a cell wall was sufficient to classify it to the genus Mycoplasma and as such it is the oldest and largest genus of the class with about half of the class ' species ( 107 validly described ), each usually limited to a specific host and with many hosts harboring more than one species, some pathogenic and some commensal.

Building codes typically classify them as ladders and will only allow them where ladders are allowed, usually basement or attic utility or storage areas not frequently accessed.

The comparison of violent crime statistics between countries is usually problematic, due to the way different countries classify crime.

For treatment purposes, doctors usually classify infectious urethritis in two categories: gonococcal urethritis, caused by gonorrhea, and nongonococcal urethritis ( NGU ).

However, hybrids between the two occur naturally where their ranges overlap, and some mammalogists classify the two as subspecies of a single species, usually treated as Vulpes velox ( with the swift fox being described as V. velox velox and the kit fox as V. velox macrotis ).

That is, the classifier is used to classify the ( usually square or rectangular ) portions of an image, at all locations and scales, as either faces or non-faces ( background pattern ).

Recent professional guidelines classify the severity of chronic kidney disease in five stages, with stage 1 being the mildest and usually causing few symptoms and stage 5 being a severe illness with poor life expectancy if untreated.

In order to use the Mahalanobis distance to classify a test point as belonging to one of N classes, one first estimates the covariance matrix of each class, usually based on samples known to belong to each class.

Most Indo-Europeanists classify Baltic and Slavic languages into a single branch, even though some details of the nature of their relationship remain in dispute in some circles, usually due to political controversies.

Pigeonholing is any process that attempts to classify disparate entities into a small number of categories ( usually, mutually exclusive ones ).

Faculty members select and evaluate important papers in their areas of expertise, usually tagging them as well to further classify papers as Clinical Trials, Novel Drug Targets etc.

Ornithologists usually classify the Eclectus Parrot as a member of tribe Psittaculini in the Psittacidae family of order Psittaciformes.

To help prevent accidental violation of these rules, the modern standard Orthodox practice is to classify food into either being meat, dairy, or neither ; the latter category is more usually referred to as parev from the Yiddish word parev ( פארעוו ) ( also spelled parve and pareve ) meaning " neutral ".

Photo sharing sites usually propose several ways to classify images.

While this will positively influence the subjective appearance of that person in real life, a still photograph usually fails to reproduce these attributes, possibly rendering a picture of the person less attractive than the real-life perception and contributing to classify that person as less photogenic.

The equipment is usually purchased from an American supplier ( although some merchants have attempted to set up shop in Canada ) and the services are billed to an American postal address.

: Boxes that are made just like traditional letterboxes, but instead of being planted in the wild, they are sent via postal mail to the people on sign up lists for the box, or around a " ring " of people in a postal ring, which is usually focused on a theme of some sort.

A post office is a facility forming part of a postal system for the posting, receipt, sorting, handling, transmission or delivery of mail, such as letters, small packages, and usually money.

The item is then processed by the postal system, where a postmark, sometimes known as a cancellation mark, is usually applied over the stamp and cover ; this procedure marks the stamp as used, which prevents its reuse.

* Definitive stamps — stamps for everyday postage and are usually produced to meet current postal rates.

* Military stamp — stamp for a country ’ s armed forces, usually using a special postal system.

Packages are often sent through some postal services, usually requiring additional postage than an average letter or postcard.

Many postal services have limits on what can and cannot be sent inside packages, usually placing limits or bans on perishable, hazardous or flammable materials.

Although postal codes are usually assigned to geographical areas, special codes are sometimes assigned to individual addresses or to institutions that receive large volumes of mail, such as government agencies and large commercial companies.

While a postcard is usually printed by a private company, individual or organization, a postal card is issued by the relevant postal authority.

There are no standard abbreviations for provinces ' names ; but the province name is optional and usually not needed if the postal code is correct.

There are always common-sense exceptions to digit grouping, such as postal codes, page numbers, and ID numbers of predefined nongrouped format, which style guides usually point out.

When these postal commodities are overprinted, they are always very carefully positioned for aesthetic appeal, usually on the blank outer border (" selvage ") of the paper.

This is usually only done when stamps are sold in large bulk quantities to businesses or other large organizations: the postal service will save the labor of cancelling each individual stamp by precancelling the entire purchased quantity.

Correspondence chess is chess played by various forms of long-distance correspondence, usually through a correspondence chess server, through email or by the postal system ; less common methods which have been employed include fax and homing pigeon.

Time limits in correspondence play are usually between 30 and 60 days for every 10 moves ( plus transmission time in postal chess ).

The Mail Art philosophy of openness and inclusion can be summed up in a few " considerations " of networking etiquette that are usually explicitly stated in the invitations ( calls ) to postal projects: a Mail Art show has no jury, no entry fee, there is no censorship, and all works are exhibited.

In the past collectors usually based their studies on " mail from ," but " mail to " and " mail through " a place expand the postal service story because outgoing mail mainly shows marking associated with the areas of study while incoming mail tells a much broader story and are now more likely to be included.

* Postal stationery are mailable products, issued by postal authorities, such as a envelopes, letter sheets, postcards, lettercards, aerograms or wrappers, on which the amount of postage has usually been pre-printed with an imprinted stamp or indicium, at the rate required for a particular postal service.

In philately, private overprints are overprints ( pictures, text, or a combination of the two ), usually rubberstamped though occasionally applied by some other method, to postage stamps ( or, occasionally, postal stationery ) used by some person or entity other than a government or other official stamp-issuing entity.

Some postal stationery envelopes contain a corner card which is a term used to describe a printed return address on the envelope, usually in the upper left hand corner.

The Derbyshire town of Swadlincote is usually given as the nearest town for the purposes of the postal service.