I am searching for an English and/or American English dictionary which enables me to search, for example
Nouns which begins/ends/includes the chunk 'exa'
Does anyone know such an online dictionary with this capabilities?
The dictionary site OneLook has search features like those. You can use wildcard symbols for letters, and limit the search to certain parts of speech as well.
Here's an example, using the parameters you put forth in your question (i.e., nouns containing
For what it's worth, 36 words were found:
(1) adnexa (2) alexandrite (3) annexation (4) counterexample (5) dexamethasone (6) exacerbation (7) exacta (8) exaction (9) exactitude (10) exactness (11) exaggeration (12) exaltation (13) exam (14) examen (15) examination (16) examinee (17) examiner (18) example (19) exanthem (20) exanthema (21) exarch (22) exarchate (23) exasperation (24) hexachlorophene (25) hexagon (26) hexagram (27) hexahedron (28) hexameter (29) hexane (30) indexation (31) inexactitude (32) inexactness (33) methotrexate (34) reexamination (35) sexagenarian (36) vexation
I can recommend you the Corpus of Contemporary American English. A Corpus is a set of texts written in a certain language. You can find many of them online and they are a very good source of research for collocations, phrasing and word choice as native speakers would do. It's not a dictionary, though. I'm afraid you can find the words there and then, if you don't know their meaning, get a dictionary to help you.
You can search for words which contain chunks like this:
For words which end in "exa"
For words which start with "exa"
For words which contain "exa"
OxfordDictionaries.com is a large dictionary that allows you to search for
*exa* and shows matching headwords.
The excellent Longman Dictionary of Contemporary English lets you search for
*exa*, but you'll notice it sometimes takes a bit longer for the page to load. That's because it's not just searching headwords, but definitions as well! So for example, physical shows up because the definition contains the word examination.
If you click 'advanced search' on Ben Zimmer's Vocabulary.com, you can search for words beginning with exa, and you can limit it to nouns, too. This has some other neat functions, like letting you search for words that rhyme with your search term, so depending on what you want, this could be very useful!
You can also search Wiktionary for words beginning with exa by searching for
exa*, but the site currently doesn't have a function to search for words ending in exa.
If you're a computer person, you can download word lists and use
grep on your own computer.