Algae – Any of various primitive, chiefly aquatic, one-celled or multicellular organisms that lack true stems, roots, and leaves but usually contain chlorophyll.  (Bottom line: includes seaweeds)

Benthic – Referring to organisms which live on or attached to the bottom of aquatic habitats.

Eulittoral - The main part of the littoral zone characterised by limpets, barnacles, mussels, fucoid algae (other than those characteristic of the littoral fringe), with red algae often abundant on the lower part. It lies above the main population of Laminariales. Zonation within the eulittoral is variable, with two to four (commonly three) belts often clearly discernible. 1) (lower) The lower belt of the eulittoral subzone, bordering the sublittoral fringe, and generally dominated by Fucus serratus and red algae. 2) (mid) The broad middle belt of the eulittoral subzone, usually characterised by limpets and barnacles or Mytilus and filamentous red algae in exposed situations, or dominated by fucoids, often with clumps of large mussels present, in shelter. 3) (upper) The narrow upper belt of the eulittoral subzone, often very variable in character. (from Hiscock, 1990).

Herbarium – A collection of dried and pressed specimens (e.g. algae and plants), systematically arranged and labeled; used for taxonomic studies.

Littoral - The area of the shore that is occupied by marine organisms which are adapted to or need alternating exposure to air and wetting by submersion, splash or spray. On rocky shores, the upper limit is marked by the top of the Littorina /Verrucaria belt and the lower limit by the top of the laminarian zone (Lewis, 1964). It is divided into separate subzones, particularly marked on hard substrata. Cf. 'intertidal'.

Macroalgae – Freshwater or marine algae that are visible to the naked eye.

Phycology – Study of algae. Synonym for algology.

Sublittoral - The zone exposed to air only at its upper limit by the lowest spring tides, although almost continuous wave action on extremely exposed coasts may extend the upper limit high into the intertidal region. The sublittoral extends from the upper limit of the large kelps and includes, for practical purposes in nearshore areas, all depths below the littoral. Various subzones are recognised (based on Hiscock, 1985.) (Cf. 'subtidal'). Also "supratidal."

Taxonomy – a system of arranging organisms into natural, related groups based on some factor common to each, as structure, embryology or biochemistry: the basic taxa now in use are, in descending order from most inclusive, kingdom, division, class, order, family, genus, and species.

Species - A category used in the taxonomic classifcation of organisms that consists of a group of similar organisms that can usually breed among themselves.

Division - A category used traditionally in the classification of plants that consists of one or several similar classes.

Class - A category used in the classification of organisms that consists of similar or closely related orders.

Order - A category used in the classification of organisms that consists of similar or closely related families.

Family - A category used in the classification of organisms that consists of similar or closely related genera.

Genus - A category used in the classification of organisms that consists of similar or closely related species.

Definitions from Oxford Dictionary of Biology and MarLIN (The Marine Life Information Network for Britain and Ireland).

Glossary of marine biology terms from MarLIN